What is the meaning and usage of the abbreviation "v. a."?

OED has under A:

15. Of various English words.
c. Grammar. In form a or (occas.) A. (a) adjective; (b) active (of a verb). Now rare.
1838 J. Bosworth Dict. Anglo-Saxon Lang. p. ccvii, v. a. or act. verb active.

So v.a. stands for verb active.

EDIT: I think the confusion here is that your first source and perhaps also your second are using the abbreviation to mean something different from what the third one is using it for.

If you look at the abbreviations in the first, and what they are used for, the v.n. abbreviation is always attached to intransitive verbs. It turns out intransitive verbs were once referred to as neuter verbs, as shown here from Webster’s Revised Unabridged Dictionary (1913):

(b) Intransitive; as, a neuter verb.

The v.a. appears to be attached to transitive verbs. It is possible that these were called active verbs because, since they took a direct object, they could be formed into a passive. It is also possible that they are contrasting them with stative verbs. The same source as referenced above gives three possibilities:

(a) Applied to a form of the verb; -- opposed to passive. See Active voice, under Voice.
(b) Applied to verbs which assert that the subject acts upon or affects something else; transitive.
(c) Applied to all verbs that express action as distinct from mere existence or state.

That source also uses v.s., which may be a stative verb, at least in the case of beis, which it says is the 3s form of to be. However, it also uses it for things like bele to burn, conteyne to continue, etc. So that may not be right.

It also has v. imp., v. impers., v. aux., and v. subst.. Considering it seems to be using v. subst. are verbs that mean “are”, the v.s. as stative is probably wrong. Besides v.n. and v.a., it has these:

• AFFERIS, EFFEIRS, v. impers.
• ARN, v. subst. Are, the third pers. plural;
• AUCHT, (gutt.) v. imp. Ought, should.
• To BECK, BEK, v. s.
• To BEIR, BERE, v. s. To roar, to make
• BEIS, v. s. Be, is; third p. sing. subj. S.
• To BELE, v. s. "To burn, to blaze."
• BENE, v. subst. Are.
• BYRD, v. imp. It behoved, it became.
• BOOST, v. imp. Behoved, was under
• BUT, v. imp. Expressive of necessity, S. of another, S. from the E. v. catch.
• To CONTEYNE, v. s. To continue.
• DOID, v. imp. It becomes, Fr. doit.
• GURDEN, v. 3 pl. Gird.
• ILD, v. imp. Would not.
• LYK, LIK, v. impers. Lyk til us, be agreeable
• MEDIS, v. impers. Avails.
• METHINK, v. impers. Methinks.
• MIRKLES, v. pl. The radical leaves of
• MOT, v. aux. May.
• MUN, v. aux. Must.
• TID, TYD, v. impers. Happened.
• WALD, v. aux.
• WAR, v. imp. War him, befal him.
• WORDIS, v. imp. It wordis, it behoves,
• 1. It worthis, v. imp. It becomes.

The third source is clearly using the abbreviation in a different way, one that means “meaning” or “roughly” or “for”. I do not think it stands for “version alternate” there, but I have been wrong before and doubtless shall soon be again.

Original posting. While v.a. does mean this, it at most applies to the third source only.

The abbreviation v.a. stands for the Latin vices agens, meaning “acting in place of”. That is, quite literally “vice agent”. Used in this way it should be read as for or meaning in English.

There is also v.a.l., which is vices agens legati, but that would not be used here.

Adolf Berger’s Encyclopedic Dictionary of Roman Law (1953) covers this and much more.

Two different abbreviations were conflated in the original question: One meaning verb active in the dictionary examples, and one possibly meaning verbis aliis, "in other words", in the Sanskrit example.

The first meaning, verb active or verbum activum, was given almost instantly by Barrie England, and then expanded upon in the answers by Andrew Leach and tchrist. Please direct your upvotes to their answers.

This is by all accounts the established meaning of "v. a.".

However, there seems to be a second meaning, verbis aliis "in other words", which is not certain, but I will make a hopefully convincing argument for it below.

By searching through other works by the same author, J. S. Speijer, I have found identical usage of "v. a." in Dutch and German publications, thus supporting a Latin origin of the abbreviation (my translations added):

• Speijer, Blijspelen van Plautus, 1887, page 55:

  sese omnes amant "zij houden slechts van zich zelf" v. a. zij zijn egoïsten [they all love themselves "they love only themselves" v. a. they are egotists]

• Same, page 106:

  vide sis "zie toch eens goed" v. a. "weet gij wel wat gij zegt?" [look, if you will "have a good look now" v. a. "do you know what you're saying?"]

• Speyer, Vedische und Sanskrit-Syntax, 1896, page 23:

  Häufig bei tiṣṭhate v. a. "jemand an­erkennen als" [Often with stands v. a. "to acknowledge somebody as"]

Note that in the last example the verb form is medio-passive, not active.

My best guess is to translate verbis aliis (or aliis verbis), the idiomatic Latin for "in other words". To anyone with a knowledge of basic Latin this will arguably be the most immediately apparent expansion. In support of this interpretation, I have found one exactly parallel use of the Dutch equivalent "m. a. w.", met anderen woorden ("in other words"), in the first book cited:

bene sit tibi! zooveel als "God zegene u!" m. a. w. "De hemel beware u daarvoor!" [may you be well! meaning as much as "God bless you!" in other words "May heaven protect you from this!"]

What's more, Speijer abbreviates the conventional et alii, "and others", as "e. a." making it possible to assume aliis being abbreviated "a." instead of the more conventional "al.".

Finally, somebody on Reddit's /r/latin independently had the same intuition as I had.

(Another suggestion vices agens was made by tchrist, drawing from Roman law vocabulary. I can not find evidence for it having generalized meaning and usage nor would this expansion be apparent to readers without a background in Roman law.)