From BiblePortal Wikipedia

Webster's Dictionary [1]

(n.) The act of imprecating, or invoking evil upon any one; a prayer that a curse or calamity may fall on any one; a curse.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [2]

an appeal to God, invoking his curse upon (1) either one's self or (2) another. For the former, (See Oath). The latter, which occurs frequently in the so-called "imprecatory Psalms" (see Edwards, On The Divine Imprecations, in the Bibliotheca Sacra, 1, 97; Presb. Quart. Rev. App. 1861; British and For. Ev. Rev. July, 1864; Heine, Abus. Psalms, 109, imprec. Helmst. 1739), is justified partly by the atrocity of some of the crimes execrated (e.g. that of Doeg), and partly by the fact of special authority in the act of inspiration. (See Accursed); (See Destruction Of Canaanites); (See Psalms).