A man dating or married to your aunt who is old enoung to be your grandpa. They tend to fall asleep at the dinner table and drone on about old people crap; Generally disliked by anyone under 40 but favoured with the Aunt's parents because of his old, old age. Can be found at local events which are free because they tend to be broke.
Niece : "OMG mom did you see Auntie Georgette's new boyfriend? Look's like we got a new gruncle!"

Mom: "Yes dear I think he is from the ice age and recently thawed out."

Niece: "I concur."

Mom: "and how!"
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When you have to take an extremely long and painful dump after eating alot.
Me: After this I'm going to take a nice gruncle.
Friend: So will i.
by The Diego Bleachers February 25, 2016
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Somebody who acts gruncley all the time.
Hey did you see Gruncle Sam yesterday he wasn't allowing me to play ram ranch.
by RussianCitizen January 26, 2020
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An uncle who keeps on gregging.
Damnnnnnn my dads brother acts like suchhhhhh a greg. What a gruncle.
by jeebneeb November 7, 2020
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Great-Uncle or Granduncle

The brother of a grandparent.
This is your Gruncle John, your Granddad's brother!
by PetticoatLane October 18, 2019
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The Cousin of another Cousin who ends up pregnant by that' cousins husbands son.
Aye yo, you heard your cousin Craig is having a baby with uncle Tonys daughter right? But ain't that her uncle? Yeah, so now it makes him a gruncle.
by MoreUrban January 12, 2023
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