1) to let or put air into (something) (aerate)

2) a written agreement by which the owner of land or a building (the lessor) agrees to let another (the lessee) have the use of it for a certain time for a fixed money payment (rent) (lease)

3) to let or bring (something) down (lower)

4) to let (leaves etc) come off, fall; to take off (clothes); to spread or send out (heat, light etc) (shed)

5) to let salvia run from the mouth (as a baby does) (slobber)

6) an opening covered with glass in a wall or roof of a building, car etc, used to let in light and air (window)