An uncertain duration of time, a period of time.
"They waited while it rained outside before deciding to leave."
In plain English: A while is an unspecified amount of time, usually meaning a short period that feels long enough to wait out something boring or difficult.
"While I was sleeping, my brother watched TV all night."
to while away the time / hours; to pass (time) idly
"The children spent their afternoon by the window, watching clouds drift across the sky while away the long summer hour."
In plain English: To while means to spend time doing something small just to pass the moments until later.
"He sat quietly in the corner while he watched everyone else leave for dinner."
During the same time that.
"While I was cooking dinner, my brother set the table."
Until.
"I will wait here while you finish your report before we leave together."
The word "while" comes from Old English hwīl, which originally meant "a short period of time." It ultimately traces back to the Proto-Indo-European root *kʷyeh₁-, meaning "to rest."