If you tuck in a piece of material, you keep it in position by placing one edge or end of it behind or under something else. For example, if you tuck in your shirt, you place the bottom part of it inside your trousers or skirt. [VP n] ⇒ 'Probably,' I said, tucking in my shirt. [V n P] ⇒ Tuck the sheets in firmly.
2. phrasal verb
If you tuck a child in bed or tuck them in, you make them comfortable by straightening the sheets and blankets and pushing the loose ends under the mattress. [V n P n] ⇒ I read Lili a story and tucked her in her own bed. [V n P] ⇒ My mother would tuck me in, turn out the lights and tiptoe out.
`There you are, me dears, just you tuck in and don't mind your manners for me.Fraser, Christine Marion NOBLE BEGINNNINGS`The teacherforgot to tuck in the ends when she shoved me on stage, quaking with fright.Hinxman, Margaret THE SOUND OF MURDER`A ship could tuck in behind the island and be protected from the North Sea.Terman, Douglas CORMORANTThen he took a moment to compose himself, run his hand down his sweat-soaked shirt, tuck in the anger and humiliation.Chuck Logan VAPOR TRAIL