fuck about

1. rude slang To engage in aimless recreation or frivolous time-wasting; to fool around. I can't believe you wasted the whole day just fucking about online.

2. rude slang To deceive or mislead someone. In this usage, a noun or pronoun can be used between "fuck" and "about." They're obviously fucking you about. There's no way a deal that good could be true.

3. rude slang To tease or play a prank on one, often by trying to get them to believe something that is not true. In this usage, a noun or pronoun can be used between "fuck" and "about." You didn't really hear a knock on the window, did you? Don't fuck me about like that! Did she really say she has a crush on me, or are you fucking about with me?

4. rude slang To joke about something. Often used in the negative to indicate absolute seriousness. Oh, come on, Tina, we're just fucking about. We didn't mean what we said. You guys, Mom is not fucking about. She said she would ground us for a month if she caught us again.