'Suck' is a common English slang term meaning that something is bad or undesirable.
Since the 1920s various constructions involving the word 'suck' have been used for fellatio, and other expressions such as 'suck hind tit' (referring to the runt of the litter being regulated to the least attractive feeding spot) and 'suck it up' (military slang meaning to pull in your gut) added to the negative connotation of the word. In the early 1970s suck broke free of its various idioms, and came to fill something akin to its current meaning. The sexual connotation remained with it for decades, but these days it is generally considered to be innocuous by the majority of the population.
Suck is, of course a verb, but it also comes in adjective form, sucky, and may occasionally be used as a noun ("that's pure suck").
Well, this writeup sucked.