Puns:Decom-posuer
NOFX misspells poseur (or poser) (once again) as posuer.
The title of this song is a pun. Here are the definitions of the two words that make up the name of this one:
Decompose:
Main Entry: de·com·pose
Pronunciation: "dE-k&m-'pOz
Function: verb
Etymology: French décomposer, from dé- de + composer to compose transitive senses
1 : to separate into constituent parts or elements or into simpler compounds
2 : ROT
intransitive senses : to break up into constituent parts by or as if by a chemical process
Poseur:
Main Entry: po·seur
Pronunciation: pO-'z&r
Function: noun
Etymology: French, literally, poser, from poser: a person who pretends to be what he or she is not : an affected or insincere person.
(Source: Merriam-Webster Online)
Time will tell us: Is she a lifer or a decom-poseur? This lyric is most likely telling the listener that only time will tell if Rose is lifer or poseur in the punk scene.