To make a very idiotic, or "jackass" assumption. Concatenation of the words "jackass" and "assume"
GF: Don't think you can hide yourself from me. I know that you're checking out that girl who you think is better looking than I am.
Me: Just because I'm looking at that girl doesn't automatically mean I'm checking her out. Maybe I just want to see if she's one of my classmates at my previous school. Maybe I'm not looking at her, but rather, the traffic that's behind her. Don't jackassume things.
by E_dawg December 26, 2008
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