Closely and firmly united, as the parts or particles of solid bodies; having the parts or particles pressed or packed together; solid; dense: as, a compact mass of people.In entomology, specifically, compacted or pressed close, as a jointed organ, or any part of it, when the joints are very closely united, forming a continuous mass: as, a compact antennal club; compact palpi.Connected or expressed with closeness or brevity, as ideas; hence, of literary style, pithy; terse; not diffuse; not verbose: as, a compact discourse.Compacted; joined; held together.Composed; consisting; made.Synonyms Firm, condensed.Terse, sententious, succinct concise.n. Structure; frame.To thrust, drive, pack, or press closely together; join firmly; consolidate, as the parts which compose a body; condense.To unite or connect firmly, as in a system; join the parts of tightly; bring into close junction, as the sheets of a book or other loose materials, by heating, pressure, or the like.To make firm or stable; establish firmly; confirm; solidify.n. An agreement; a contract between parties; in general, any covenant or contract between individuals, members of a community, or nations.United in a compact; leagued; confederated.To make a contract or enter into an agreement.In petrography, dense without pores: also applied to extremely fine-grained textures in which the individual crystals or grains cannot be seen by the unaided eye: equivalent to aphanitic, cryptocrystalline, and cryptoclastic.