Expressions (phrases, clauses, etc.), Godan verb with 'su' ending
to go over the top; to act without restraint; to cut loose
Idiomatic expression
休みの前などは少し羽目を外して飲むのだが、杜仲茶割りで飲むと二日酔いが全くない。I usually cut loose a bit and drink plenty before a day off work, but if my drinks are cut with tochu tea, then I get absolutely no hangover.
Also written ハメを外す【はめをはずす】