On Facebook or Instagram, when you click "like" by mistake. This usually can happen when trying to scroll up or down the page on a touchscreen device with your finger
and accidentally clicking "like" on a Facebook status or Instagram photo. This can sometimes cause embarrassment.
Originates from the phrase "butt dial" which means to dial someone by mistake with your cell phone; Usually caused by accidentally bumping "dial" with your butt while your phone is in your back pocket.
I didn't mean to butt like that stupid picture my friend posted on Instagram. Now everyone thinks I like pictures of kittens. How embarrassing.
I think I just butt liked someone's status update when I was trying to scroll on my iPhone. I haven't spoken to that person in years. How awkward.