n. [OE. quarel, OF. quarrel, F. carreau, LL. quadrellus, from L. quadrus square. See Quadrate, and cf. Quadrel, Quarry an arrow, Carrel.] 
1. An arrow for a crossbow; — so named because it commonly had a square head. [Obs.] “To shoot with arrows and quarrel.” Sir J. Mandeville. “Two arblasts, … with windlaces and quarrels.” Sir W. Scott. 
2. (Arch.) Any small square or quadrangular member; as: (a) A square of glass, esp. when set diagonally. (b) A small opening in window tracery, of which the cusps, etc., make the form nearly square. (c) A square or lozenge-shaped paving tile. 
3. A glazier’s diamond. Simmonds. 
4. A four-sided cutting tool or chisel having a diamond-shaped end.