noun

• (historical, obsolete) Alternative form of fu: an administrative subdivision of imperial China; the capital of such divisions.

noun

• (programming) A metasyntactic variable used to represent an unspecified entity. If part of a series of such entities, it is often the first in the series, and followed immediately by bar.
  "Suppose we have two objects, foo and bar."
• (fandom slang) Alternative letter-case form of Foo (“placeholder god”).

noun

• (slang) Pronunciation spelling of fool.
  "[page 10:] "I knew you'd be scared," Reggie laughed. "What are you doin', foo? You must be crazy. You don't scare me." "Then why did you almost fall out of that chair? I scare everyone." [page 38:] "This is coo," said Fred. "It's almost like being there." "We are there, foo!" said Reggie as the boys slapped palms."

name

• (dated, fandom slang, humorous) A mock deity of early science fiction fandom; a fannish ghod.
  "Robert Bloch has blown his top. Backwards or forwards (or sideways) Foo ((ugh)) and Ghu ((!)) cannot be united! Does one eat chocolate cake with catsup on it? If you do and enjoy it then go off and be a fooghuist in your own little corner. You may as well worship Roscoe. Or Alpaugh. Foo fans are happy fans. Ghu isn't really helping Hoffman put out a fine mag you know. The fans who read Q are probably -- for the most part -- Foofooists."