look up anything, like your first name:
1. thats what your mum said
To piss someone off, royally.
"Ow, i'm in pain"
"That's what your mum said."
by -Ben- Mar 14, 2005 add a video
2. thats what your mum said
a phrase to follow any word or sentence whether it makes sense or makes u look like a fuckin tool, said whenever someone speaks to you or anyone within hearing distance.
"hey man u comin to the shops"
"thats what ur mum said"
"mate, ur a fuckin tool"
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