The Collaborative International Dictionary of English v.0.48:
Dirigible \Dir"i*gi*ble\, a. Capable of being directed; steerable; as, a dirigible balloon. [1913 Webster]WordNet (r) 3.0 (2006):
dirigible adj 1: capable of being steered or directed [syn: steerable, dirigible] n 1: a steerable self-propelled aircraft [syn: airship, dirigible]