Granddaddy

noun, slang

Definitions

Noun
  1. 1
    A grandfather. informal
  2. 2
    the father of your father or mother wordnet
  3. 3
    Something that is the greatest or most significant of its kind. informal

    "The nature of this gas enables it to absorb the majority of the sun's ultraviolet rays, thus saving the human race from the granddaddy of all sunburns."

Etymology

From grand- + daddy.

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