Lying in is a phrase that refers to someone being in a horizontal position or resting in bed. There are several synonyms for the phrase that can be used interchangeably. Some of these synonyms include reclining, resting, lounging, stretching out, and lying down. In addition to these synonyms, there are also phrases that can be used to convey the same idea, such as taking a nap, getting some shut-eye, or relaxing. Regardless of the specific word or phrase used, the idea of lying in typically implies a sense of relaxation or a need for rest. It is a common phrase that is often used in everyday conversation and has many synonyms to choose from.