look up any word, like tribbing:
 
1.
Pretending To Laugh So You Dont Feel Stupid

--used as an alternate to "lol" when something isnt actually funny
ptlsydfs is commonly used in instant messaging :

abcXdef: funny story!

cbaXfed: ok.

abcXdef: so at lunch, jane found a quarter, and i made her give it to me! lol!

cbaXfed: : ptlsydfs

abcXdef: good times!

cbaXfed: ...