"Bags it" is a term used to denote the act of claiming or reserving something for oneself. It is not an antonym, but rather a colloquial phrase. However, when it comes to antonyms for "bags it", the opposite could be "leaves it" or "gives it up". Both of these terms imply that one is relinquishing their claim or reservation of something. Another antonym could be "forfeits it", which implies that one has lost their right or claim to something they previously held. Thus, while "bags it" is not an antonym itself, there are several antonyms that one could use in response to this phrase.