hairy: adj. 1. Annoyingly complicated. "{DWIM} is incredibly hairy." 2.

:hairy: adj. 1. Annoyingly complicated. "{DWIM} is incredibly
hairy." 2. Incomprehensible. "{DWIM} is incredibly hairy."
3. Of people, high-powered, authoritative, rare, expert, and/or
incomprehensible. Hard to explain except in context: "He knows
this hairy lawyer who says there's nothing to worry about." See
also {hirsute}.

A well-known result in topology called the Brouwer Fixed-Point
Theorem states that any continuous transformation of a surface into
itself has at least one fixed point. Mathematically literate
hackers tend to associate the term `hairy' with the informal
version of this theorem; "You can't comb a hairy ball smooth."

The adjective `long-haired' is well-attested to have been in
slang use among scientists and engineers during the early 1950s; it
was equivalent to modern `hairy' senses 1 and 2, and was very
likely ancestral to the hackish use. In fact the noun
`long-hair' was at the time used to describe a person satisfying
sense 3. Both senses probably passed out of use when long hair
was adopted as a signature trait by the 1960s counterculture,
leaving hackish `hairy' as a sort of stunted mutant relic.
-- The AI Hackers Dictionary