Let1  —v. (-tt-; past and past part. Let) 1 a allow to, not prevent or forbid. B cause to (let me know). 2 (foll. By into) allow to enter. 3 grant the use of (rooms, land, etc.) For rent or hire. 4 allow or cause (liquid or air) to escape (let blood). 5 aux. Supplying the first and third persons of the imperative in exhortations (let us pray), commands (let it be done at once; let there be light), assumptions, etc. (let ab equal cd). —n. Act of letting a house, room, etc.  let alone 1 not to mention, far less or more (hasn't got a television, let alone a video). 2 = let be. Let be not interfere with, attend to, or do. Let down 1 lower. 2 fail to support or satisfy, disappoint. 3 lengthen (a garment). 4 deflate (a tyre). Let down gently reject or disappoint without humiliating. Let drop (or fall) drop (esp. A word or hint) intentionally or by accident. Let go 1 release. 2 a (often foll. By of) lose one's hold. B lose hold of. Let oneself go 1 act spontaneously. 2 neglect one's appearance or habits. Let in 1 allow to enter (let the dog in; let in a flood of light). 2 (foll. By for) involve (a person, often oneself) in loss or difficulty. 3 (foll. By on) allow (a person) to share a secret, privileges, etc. Let loose release, unchain. Let off 1 a fire (a gun). B explode (a bomb). 2 allow or cause (steam etc.) To escape. 3 a not punish or compel. B (foll. By with) punish lightly.