gorilla arm
n. The side-effect that destroyed touch-screens as a
mainstream input technology despite a promising start in the early
1980s. It seems the designers of all those
spiffy touch-menu
systems failed to notice that humans aren't designed to hold their
arms in front of their faces making small motions. After more than
a very few selections, the arm begins to feel sore, cramped, and
oversized; hence `gorilla arm'. This is now considered a classic
cautionary tale to human-factors designers; "Remember the gorilla
arm!" is shorthand for "How is this going to fly in *real*
use?".
