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1.
The more common spelling of a very hilarious Irish surname; see McGillicutty. Makes a good filler word, especially for proper names.
My name is Bumpus McGillicuddy and I am a traveling novelty salesman.
by Bumpus McGillicuddy April 20, 2007
 
2.
A name to tag on to an adjective to show the severity of the aforementioned word.
When your nose won't quit running and your full of mucous,
" I'm Snotty McGillicuddy" or when your friend is in a foul mood,
" Why are you being such a crabby McGillicuddy?"
by shelly G June 01, 2007
 
3.
A term used by a drunk individual as they slur their words when he/she is refering to a certain person or the actions of a person.
1. Steve: Get out of here man! your not allowed in!

Taylor: Hands off grabsy McGillicuddy!

2. Ron: Hey man, I just got accepted to Uni for engineering!

Taylor: Well look at you smartsy McGillicuddy!
by Francois98 October 03, 2009
 
4.
To get one's balls tickled
Yo dude, last night Jessica gave me a wicked McGillicuddy. I was laughing so hard.
by Josh Kokonut May 25, 2011