From Longman Dictionary of Contemporary Englishlet somebody/something into something phrasal verb1TELL A SECRETto tell someone something that is secret or privateIt was time to let the rest of the family into the secret.2technicalTBC to put something such as a window or a decoration into a wallTwo large windows were let into the wall each side of the door. Grammar Let into is usually passive in this meaning. →let→ See Verb table
Examples from the Corpus
let into • Would you let that man into any house you owned?• You saw the shadow of the mountain and you let it into the cave and the fire has gone out.• When she let herself into the flat, Ralph was waiting in the hall.• They went down the steps and let themselves into the flat.• Did you let her into the house?• Cathy went into the shop and Wycliffe let himself out into the little hall from which stairs led up to the flat.• He had let him into the Mezvinski tomb, brought him some rags for cover.• If the ionchannellets positive ions into the receivingneuron, the neuron is pushed toward firing.