From The Collaborative International Dictionary of English v.0.48:
Composure \Com*po"sure\, n. [From Compose.] 1. The act of composing, or that which is composed; a composition. [Obs.] [1913 Webster]
Signor Pietro, who had an admirable way both of composure [in music] and teaching. --Evelyn. [1913 Webster]
2. Orderly adjustment; disposition. [Obs.] [1913 Webster]
Various composures and combinations of these corpuscles. --Woodward. [1913 Webster]
3. Frame; make; temperament. [Obs.] [1913 Webster]
His composure must be rare indeed Whom these things can not blemish. --Shak. [1913 Webster]
4. A settled state; calmness; sedateness; tranquillity; repose. "We seek peace and composure." --Milton. [1913 Webster]
When the passions . . . are all silent, the mind enjoys its most perfect composure. --I. Watts. [1913 Webster]
5. A combination; a union; a bond. [Obs.] --Shak. [1913 Webster]