a clock which is regulated by a quartz crystal

(Britain) a small triangular side window in a motor car

(physics) a sheet of birefringent material whose thickness is such that the light associated with the larger refractive index is retarded in phase by 90° with respect of that associated with the smaller refractive index; used to convert linearly polarized light into circularly polarized light

Having or displaying half the mental capacity of a half-wit.

(mineralogy) Any form of diorite containing appreciable amounts of quartz.

(US) a county court held every three months.

A crack in a horse's forefoot; a sand crack.

(Canada, US, music) A musical note one beat long in 4/4 time.

(astronomy) Either of the intermediate stages between the new and full moons.

(Britain) Each of the four days customarily regarded as starting a new quarter year, on which rents etc are often due.