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."