capsuleEnglishOxford American Thesauruscapsule noun 1 he placed a capsule under his tongue: pill, tablet, lozenge, pastille, pilule, drop, caplet, pellet, bolus, troche; informal tab. 2 the bottle's capsule is lead-free: cover, seal, cap, top. 3 a space capsule: module, craft, probe; detachable compartment, section. 4 sow small pots with two or three capsules: seed case, pod, shell, husk, hull, case, sheath; technical pericarp, exocarp, legume, integument.