Ah, could be my favourite word in the English language. It's a crude word and not especially polite but I wouldn't say it's really offensive. I don't find it offensive at all but maybe that's just me. In addition to meaning nonsense/rubbish it's a slang word for 'testicles.' It is also used as an exclamation when something goes wrong. Say I am carrying a box of staples and I drop them on the floor so they spill everywhere, I might say 'bollocks!' to express my frustration (this happened this morning to me so rather apt. And yes I did use that word when I dropped them)

It is a very RUDE slang word for "nonsense" or "rubbish". For example, if you want to disagree with what someone has said you can say. "That's a lot of bollocks" .But I DO NOT recommend that you use this in conversation. It is very offensive.