Green’s Dictionary of Slang

poss (out) v.

[Irish poss, to dash or shake violently in water; ult. may be Fr. pousser, to push]

(Irish) to wash; thus possing wet adj., very wet; posser n., one who gets wet.

[Ire]Joyce Ulysses 341: When she undid the strap she cried out, holy saint Denis, that he was possing wet.
[Ire]C. Brown Down All the Days 107: Sean – you blondey bastard – keep out while I poss out the floor!
[Ire]P. O’Keeffe Down Cobbled Streets, A Liberties Childhood 15: She was a generous and loving person and did not mind at all all the slopping and possing out of baby clothes. [Ibid.] 116: You’ll have my good kitchen floor possin’ wet with your andremartins.
[Ire]G. Coughlan Everyday Eng. and Sl. [Internet] Posser (n): when you get a wet foot from walking in a puddle of water.