The Jargon File (version 4.4.7, 29 Dec 2003):

pico-
 pref.

    [SI: a quantifier meaning ? 10^-12] Smaller than nano-; used in the same
    rather loose connotative way as nano- and micro-. This usage is not yet
    common in the way nano- and micro- are, but should be instantly
    recognizable to any hacker. See also quantifiers, micro-.


The Free On-line Dictionary of Computing (30 December 2018):

prefix
atto-
exa-
femto-
giga-
kilo-
mega-
micro-
milli-
peta-
pico-
tera-
yocto-
yotta-
zepto
zetta-

   1.  An SI prefix used to multiply the value of an SI
   (Système International) unit by some power of ten.

   2.  In mathematics or programming, a
   prefix operator is one that is written before its operand.  In
   a programming language using prefix notation, all operators
   are prefix operators.

   (2014-07-08)