When your niece or nephew becomes a parent, you become a great uncle, a gruncle.
My niece had a baby girl and now I am Gruncle Bob.
Another way of saying "Great Uncle" (your grandparent's sibling)
Gruncle is coming over for dinner tomorrow, I hear he knows how to steal noses.
A gruncle occurs in the very freaky situation when your uncle, the brother of your father or mother, marries your grandmother, the mother of the opposite parent.
Roger's uncle, his father's brother, married his grandmother, his mother's mother. Roger's uncle is now his gruncle
An awesome great uncle
Dude, I love your gruncle!
Gord got to hold his neice for the first time tonight.
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!"