n. An opening; an aperture; a gap; a chasm.n. In anatomy, a foramen.n. In grammar and prosody, the coming together of two vowels without intervening consonant in successive words or syllables of one word.n. A space from which something requisite to completeness is absent, as a missing link in a genealogy, an interval of unknown history, a lost or erased part of a manuscript, etc.; a lacuna; a break.n. Specifically, in logic, a fault of demonstration, consisting in the omission to prove some premise made use of, and not self-evident or admitted.