Originally of mortar shells, etc.; modern sense of "explosive device placed by hand or dropped from airplane" is from 1909. Meaning "old car" is from 1953. Meaning "success" is from 1954 (late 1990s slang the bomb "the best" probably is a fresh formation); opposite sense of "a failure" is from 1961. The bomb "atomic bomb" is from 1945. Compare shell (n.).
a type of laser that emits microwaves, 1955, acronym from "microwave amplification (by) stimulated emission (of) radiation." Related: Mase (v.).
1912 in reference to the system of education through free but guided play that was devised 1907 by Italian educationist Maria Montessori (1870-1952).
In reference to devices, the sense of "behaving as though guided by intelligence" (as in smart bomb) first attested 1972. Smarts "good sense, intelligence," is first recorded 1968 (Middle English had ingeny "intellectual capacity, cleverness" (early 15c.)). Smart cookie is from 1948.