‖ [ L., one half more, one and a half. ] (Chem.) A combining form (also used adjectively) denoting that three atoms or equivalents of the substance to the name of which it is prefixed are combined with two of some other element or radical; as, sesquibromide, sesquicarbonate, sesquichloride, sesquioxide. [ 1913 Webster ]

☞ Sesquidupli- is sometimes, but rarely, used in the same manner to denote the proportions of two and a half to one, or rather of five to two. [ 1913 Webster ]

a. Sesquialteral. [ 1913 Webster ]

{ } n. [ NL. sesquialtera. ] (Mus.) A stop on the organ, containing several ranks of pipes which reenforce some of the high harmonics of the ground tone, and make the sound more brilliant. [ 1913 Webster ]

{ } a. [ L. sesquialter once and a half; sesqui- + alter other: cf. F. sesquialtére. ] Once and a half times as great as another; having the ratio of one and a half to one. [ 1913 Webster ]

Sesquialteral ratio (Math.), the ratio of one and a half to one; thus, 9 and 6 are in a sesquialteral ratio. [ 1913 Webster ]

a. Sesquialteral. [ 1913 Webster ]

a. [ Sesqui- + basic. ] (Chem.) Containing, or acting as, a base in the proportions of a sesqui compound. [ 1913 Webster ]

a. [ Sesqui- + duplicate. ] Twice and a half as great (as another thing); having the ratio of two and a half to one. [ 1913 Webster ]

Sesquiduplicate ratio (Math.), the ratio of two and a half to one, or one in which the greater term contains the lesser twice and a half, as that of 50 to 20. [ 1913 Webster ]

n. [ Sesqui- + oxide. ] (Chem.) An oxide containing three atoms of oxygen with two atoms (or radicals) of some other substance; thus, alumina, Al2O3 is a sesquioxide. [ 1913 Webster ]

{ } a. [ Sesqui- + pedal: cf. F. sesquipédal, L. sesquipedalis. ] Measuring or containing a foot and a half; as, a sesquipedalian pygmy; -- sometimes humorously applied to long words. [ 1913 Webster ]

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{ } n. Sesquipedality. [ 1913 Webster ]