godan verb (-su), transitive verb
drink the night away; drink until dawn
Describes spending the whole night drinking, often in a social setting. The focus is on the passage of time while drinking, not necessarily on getting drunk.
昨夜は友達と飲み明かした。
Last night I drank the night away with friends.
週末はよくバーで飲み明かす。
On weekends I often drink until dawn at a bar.