Define: Load Average

Written by  on Juli 1, 2007

The loadaverage is represented as the average number of runable jobs (the sum of the run queue length and the number of jobs currently running) over the last one, five and fifteen minutes.

– System Performance Tuning, O'Reilly Media

UNIX® Load Average Part 1: How It Works

Finer details on "load avergaes"

Update: Linux Load Average -Not Your Average Average