The American Heritage® Dictionary of the English Language, 4th Edition
n. The father of one's mother or father.
n. A forefather; an ancestor.
v. To exempt (one involved in an activity or business) from new regulations: The new ordinance restricts the size of billboards, but it grandfathers those erected before 1997.
v. To retain existing laws or rules only for those people or organisations that were previously affected by them, and apply new laws or rules to the unaffected people or organisations.
the GNU version of the Collaborative International Dictionary of English
n. A father's or mother's father; an ancestor immediately after the father or mother in lineal ascent.
The Century Dictionary and Cyclopedia
n. A father's or mother's father; an ancestor in the next degree above the father or mother in lineal ascent: correlative to grandson, granddaughter, and grandchild.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the father of your father or mother
Word Usage
"For example, whereas the Hebrew phrase for my grandfather' was sav-í grandfather + 1st person singular possessive', in Israeli it is sába shel-ì grandfather of me'."