Whilst is defined as while and refers to things going on at the same time as something else.
(conjunction)If you fall asleep as you are watching a movie, this is an example of a situation where you fall asleep whilst watching a movie.
See whilst in Webster's New World College Dictionary
conjunction
Origin: ME whilest, extended < whiles, whiles
See whilst in American Heritage Dictionary 4
conjunction
Origin:
Origin: Middle English whilest
Origin: , alteration of whiles, whiles; see whiles
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