A twerp is someone who's annoying or foolish.
When people say that someone is being a twerp, they usually mean that this person is acting silly, making jokes that aren't funny, or saying something that doesn't make sense. It's like when you're trying to have a serious conversation with your friend and then he starts cracking terrible dad jokes – it can be frustrating! Using the word "twerp" is a lighthearted way to express that feeling.
(UK) A fool, a twit.
Example: Now you've broken it, you twerp!
