is an attempt to decrease
of an entity exhibiting
by providing a noxious
or unpleasant stimulus
when that behavior
A layman's example: yelling at someone for leaving the toilet seat up.
It's really pretty ineffective when compared to positive reinforcement but there are situations in which it may be the best tool available, especially if there's no alternate behavior presented which is preferable.
Positive punishment is often referred to as negative reinforcement by lay-folk. This may be a situation in which positive punishment is called for.