Coucher is a French term that refers to the act of going to bed or lying down. There are several synonyms for this term, including se coucher, s'allonger, se mettre au lit, se reposer, dormir, and se detendre. Se coucher means to go to bed, while s'allonger refers to lying down. Se mettre au lit means to get into bed, and se reposer means to rest. Dormir simply means to sleep, and se detendre means to relax. Each synonym has a slightly different connotation and usage, but all relate to the act of resting in some way.