Not good. Bad.

The early Jazz musicians would say that a guy could really "Blow" if he had a good sound when playing the horn. If he couldn't play very well then they would say that he was "Sucking" on that horn. That's where the term "Suck" as being something bad came from.

He plays that horn so poorly that he must be sucking on it.

He doesn't blow, he sucks.

If you suck, it generally means you have no skill and/or talent.

Oddly enoguh, even though suck is the opposite of blow, blow is an insult also.

Damn you suck at sports.

1)A term meaning bad or not good

2)To put ones mouth over another object and pull air back. Often done in sexual ways.

1)Abby: I can't go to homecoming!
Rebecca: Wow. That sucks.

2)Camille sucks Mark's cock every night.

(for those under 30 years old) An intransitive verb indicating a negative state of affairs. Could be poor performance, bad weather, illness, general dislike, or any of innumerable negative thoughts.

(for those over 30 years old) Always a transitive verb. Colloquially used as shorthand for suck dick with noun dick understood. Synonymous with blow and bite. Used as an insult; indicates homosexuality.

(under 30) Cracka 1: Hey did you see the Simpson's last night? Bart said his father sucks!!!
Cracka 2: So, what's your point?

(over 30) Son: Gee dad, I don't want to do my homework. Math sucks.
Father: You're grounded for a week, you perverted little delinquent. And wash your mouth out with soap.

to be really really crappy

That team last night really sucked. They just plain sucked. I've seen teams suck before, but they were the suckiest buncha sucks that ever sucked.

No good.

I just lost my watch. That really sucks!

the new york yankees!

the yankees suck!