Named after the purple blob Maccas character who does not resemble anything in real life but seems to have an affinity for milkshakes.
"Too late, I already grimmed mine"
2 - "Where's the toilet otherwise I'm going to grim my pants"
It's usually a girl who loves boys and is always around them, she sucks dick and has sex and does lots of stuff with lots of different boys.
Just another way of saying a prostitue but even worse.