Is this consider sexual assault?

I was at my friend house and her brother was in the hallway and the hallway is very skinny so I had to go past him facing forward and when I was going past him he grab my butt and was staring into my eyes the whole time And I backed up and walked away and he follow me into their backyard we’re my friend was is thay sexual assault you think or did he get the wrong idea when i walk past him?
Is this consider sexual assault?
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