The Collaborative International Dictionary of English v.0.48:

Sigillum \Si*gil"lum\, n.; pl. Sigilla. [L.] (Rom. & Old Eng.
   Law)
   A seal.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

SIGILLUM. A seal. (q.v.) Vide Scroll.