Word or phrase for clumsy, inaccurate expression

I'm seeking a word or phrase useful for referring to a bad sentence which clumsily, inaccurately and ambiguously attempts to express an idea or concept.

Bad-sentence example: "We do a multiplication of 60 of the 10^10 terms to get us to 10^600 and then a multiplication of 10^3 terms to reach 10^603."

Phrases incorporating 'mangled', 'tortured ', 'muddled' and 'still-born' may resemble what I want, but seem overly judgmental.

Update (Response to questions about example; with 'infelicity' and 'solecism' adopted from an answer)

Inaccurate -- The sentence (from a sci.math newsgroup posting by "AP") is inaccurate or misleading in first using the "multiplication of ..." infelicity one way for the (10^10)^60 calculation, and then a different way for the (10^600)*(10^3) calculation. That is, if the first case means (10^10)^60, the second might be thought to mean either (10^10)^(10^3) or (10^600)^(10^3).

Clumsy -- The solecisms "a multiplication of 60 of the 10^10 terms to get us to 10^600" and "a multiplication of 10^3 terms to reach 10^603" are longwinded and ambiguous ways to say "compute 10^600 as the 60th power of 10^10" and "compute 10^603 as (10^600)*(10^3)".

You might be looking for

solecism |ˈsäləˌsizəm, ˈsō-|
noun
a grammatical mistake in speech or writing.

or possibly

malaprop |ˈmaləˌpräp|(also malapropism )
noun
the mistaken use of a word in place of a similar-sounding one, often with unintentionally amusing effect, as in, for example, “dance a flamingo ” (instead of flamenco).

or perhaps my personal favorite

infelicity |ɪnfɪˈlɪsɪti|
noun ( pl. infelicities )
1 a thing that is inappropriate, especially a remark or expression: she winced at their infelicities and at the clumsy way they talked.

(All citations from NOAD.)

I usually use the word obscure to refer to an ambiguous and overly verbose sentence.

Pending the clarification of your question here's a brief exposition of mechanisms that might be at play here:

You ask for a single term that describes 'clumsiness, inaccuracy and ambiguity', however usually such erroneous properties are classified into two categories: stylistic vices and (logical) fallacies.

Ambiguity as fallacy is well defined here (and I feel it might cover inaccuracy as well).

Clumsiness on the other hand is a very vague term which can be aided by any number of stylistic vices, listed here.

Single term might be possible, but you will have to be more precise or be satisfied with general terms such as 'muddled' that you propose yourself. If this is the course that you want to take, which might not be more judgmental than the more exact classifications presented above, but is definitively harder to argue for, you should look at synonyms of

• ambiguous eg. cryptic, dubious, enigmatic, equivocal, inconclusive, indefinite, indeterminate, inexplicit, muddy, multivocal, obscure, opaque, polysemous, puzzling, questionable, tenebrous, uncertain, unclear, unintelligible, vague
• inaccurate eg. careless, counterfactual, defective, discrepant, fallacious, false, faulty, imprecise, in error, incorrect, inexact, mistaken, off, off base, unreliable, unsound, wrong
• clumsy¹ eg. blundering, bulky, bumbling, bungling, butterfingered, clownish, crude, elephantine, gauche, gawkish, gawky, graceless, ill-shaped, incompetent, inelegant, inept, ponderous, stumbling, unadept, uncoordinated, uncouth, uneasy, ungainly, unhandy, unskillful, untactful, untoward, weedy

out of which it might be the safest to go with unclear.

¹ The antonyms of 'clumsy' are more subjective as it might be expected, since 'clumsy' itself is essentially less objective than the terms 'ambiguous' and 'inaccurate'. You might want to ignore them if you are striving not to be perceived as judgmental.

Also, do look at the synonyms of synonyms, too. There is a myriad of terms that might apply, depending on what you actually need.

Possible options:

• confusing; abstruse
• incoherent; inarticulate
• tongue-tied; word-bound (about a speaker and not a phrase, though)
• cumbersome

Sorry, for my ham-fisted attempt at an earlier post...i still feel it's appropriate in response to to the initial query