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. There is a theorem in simplicial homology theory which states that any continuous tangent field on a 2-sphere is null at least in a 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. (Previous versions of this entry associating the above informal statement with the Brouwer fixed-point theorem were incorrect.) 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. In British mainstream use, hairy means dangerous , and consequently, in British programming terms, hairy may be used to denote complicated and/or incomprehensible code, but only if that complexity or incomprehesiveness is also considered dangerous.