I heard many people said suck in various situations. I probably know it's not a good word to describe someone or something. Here are some meaning of suck i have collected:
1/ an object that you lack of skill or talent = no good at [something]
Ex: he's suck at baseball.
2/ opposite of blow
Ex: suck on straw
3/ to steal/ rob something
Ex: I got sucked my iphone last night.
4/ a person that insanely lame
Ex: Tom's telling Jay what to do in bed.
jay: you're suckkkkkkkkk.
5/ short form for "you suck dick" = you're gay
Ex: Lil' Timmy: Dave, you suck at hopescotch.
Dave: Frig off, Timmy - you are so gay.
6/ an exlaimation of anger or exasperation
Ex: suck! I forgot my homework.
7/ to give someone head???
8/ and something in sexual activity .. probably no good to say.
Be careful when you say words that you're not sure about .. unless you want to start a fight or want others to be misunderstand you. You might saying bad word if you don't even know that word you're saying is a bad word lolz.
p/s I myself don't really got this "suck" word