barn

n. [uncommon; prob. from the nuclear military] An unexpectedly large
quantity of something: a unit of measurement. Why is /var/adm taking up so
much space? The logs have grown to several barns. The source of this is
clear: when physicists were first studying nuclear interactions, the
probability was thought to be proportional to the cross-sectional area of
the nucleus (this probability is still called the cross-section). Upon
experimenting, they discovered the interactions were far more probable than
expected; the nuclei were as big as a barn. The units for cross-sections
were christened Barns, (10 -24 cm 2 ) and the book containing cross-sections
has a picture of a barn on the cover.