Lewis & Short

assŭla (in many MSS. astŭla), ae, f. dim. [axis].

  1. I. A splinter, shaving, chip: at etiam cesso foribus facere hisce assulas, Plaut. Merc. 1, 2, 20: Melandrya vocantur quercūs assulis similia, Plin. 9, 15, 18, § 48: assula tenuis brevisque, id. 16, 11, 22, § 54.
    Of marble, a chip, shiver, Vitr. 7, 6.
  2. * II. A shingle, σχίδη: Bibacul. ap. Suet. Gram. 11.