Definition of let in
1 : to insert or embed in (a surface) lets in diagonal sheathing at each corner of the house
2 : to involve or commit unfavorably the provisions … could still let us in for trouble — Elmer Davis smiled at all her schemes, little dreaming that … she was letting him in for some £20,000 — Elizabeth Montizambert
3 : to share information with or allow to participate learned a lot more … and I'll let you in on it — Rex Ingamells
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