micro-: pref. 1. Very small; this is the root of its use as a quantifier prefix

:micro-: pref. 1. Very small; this is the root of its use as a
quantifier prefix. 2. A quantifier prefix, calling for
multiplication by 10^(-6) (see {{quantifiers}}). Neither
of these uses is peculiar to hackers, but hackers tend to fling
them both around rather more freely than is countenanced in
standard English. It is recorded, for example, that one
CS professor used to characterize the standard length of his
lectures as a microcentury --- that is, about 52.6 minutes (see
also {attoparsec}, {nanoacre}, and especially
{microfortnight}). 3. Personal or human-scale --- that is,
capable of being maintained or comprehended or manipulated by one
human being. This sense is generalized from `microcomputer',
and is esp. used in contrast with `macro-' (the corresponding
Greek prefix meaning `large'). 4. Local as opposed to global (or
{macro-}). Thus a hacker might say that buying a smaller car to
reduce pollution only solves a microproblem; the macroproblem of
getting to work might be better solved by using mass transit,
moving to within walking distance, or (best of all) telecommuting.
-- The AI Hackers Dictionary