Definitions for half-hour
Random House Webster's College Dictionary
a period of 30 minutes.
the midpoint of an hour, as 12:30.
(adj.)of, pertaining to, or consisting of a half-hour.
Origin of half-hour:
half-hour, 30 minutes(noun)
a half of an hour
A period of time equal to thirty minutes.
The time of thirty minutes past any particular hour.