What part of speech is 'pooped' in "I am pooped"

I have a wager that 'pooped' in "I am pooped" is not an adjective; however the betting party contends that it is an adjective since "it describes the state of the subject, I".

The other party also cites the wictionary entry for pooped as evidence.

I have found evidence that pooped is used as a verb, such as this CMU automated grammar parser; however the grammar parser concedes it is guessing at the part of speech (note the [!]) in the output...

++++Time                                          0.00 seconds (59.77 total)
Found 1 linkage (1 with no P.P. violations)
  Unique linkage. cost vector = (UNUSED=0 DIS=0 AND=0 LEN=3)

 +-SX-+---Pv--+
 |    |       |
I.p am.v pooped[!].v 

Constituent tree:

(S (NP I)
   (VP am
       (VP pooped)))

Could someone explain the part of speech that 'pooped' is above, as well as the rationale for choosing this response?

Solution 1:

Pooped when used as a verb is a synonym for "to defecate". For example: "I pooped in the bathroom." In the sentence you're asking about, though, "pooped" is definitely used as an adjective. This is because the verb "to be" is a copulative verb (more commonly known as a linking verb), and copulative verbs by nature link a noun or adjective to the subject. For example, if we modified the above sentence to "I am happy", it is in meaning "I = happy". Now we know that it is either a noun or an adjective, but (to me at least) it is clear that "pooped" isn't a noun, as one can't say "I have a pooped in my backpack".
So your answer is, it's an adjective.

Solution 2:

As defined by the Cambridge Dictionary Online, pooped is an adjective meaning

very tired:

Students are pooped because they’re juggling classes, studying, and jobs.

Similarly, the Collins Dictionary defines it as

exhausted

The boys are too pooped to fight.

It has been in use for some time. Webster's Revised Unabridged Dictionary (1913) defines it as

Tired; exhausted, fatigued