subsonic

adj (flying at a speed) less than the speed of sound 亚音速（飞行）的: a subsonic speed, aircraft, flight 亚音速、 亚音速飞机、 亚音速飞行. Cf 参看 supersonic.

subsequence, subsequent, subsequent to, subsequently, subservience, subservient, subserviently, subside, subsidence, subsidiary, subsidization, subsidization, subsidisation, subsidize, subsidize, subsidise, subsidy, subsist, subsistence, subsistence crop, subsistence level, subsoil, substance, substandard, substantial, substantially, substantiate, substantiation, substantive, substantively, substation, substitute, substitute for, substitute...for, substitution, substratum, substructure, subsume, subtenancy, subtenant, subtend, subterfuge,