hiatus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A gap or interruption in space, time, or continuity; a break: "We are likely to be disconcerted by . . . hiatuses of thought” ( Edmund Wilson).
2. n. Linguistics A slight pause that occurs when two immediately adjacent vowels in consecutive syllables are pronounced, as in reality and naive.
3. n. Anatomy A separation, aperture, fissure, or short passage in an organ or body part.

Century Dictionary and Cyclopedia

1. n. An opening; an aperture; a gap; a chasm.
2. n. In anatomy, a foramen.
3. n. In grammar and prosody, the coming together of two vowels without intervening consonant in successive words or syllables of one word.
4. 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.
5. 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.

Wiktionary

1. n. A gap in a series, making it incomplete.
2. n. A syllable break between two vowels, without an intervening consonant. (Compare diphthong.)
3. n. The condition of having such a break.
4. n. Words like reality and naïve contain vowels in hiatus.
5. n. A gap in geological strata.
6. n. An opening in an organ.
7. n. An interruption, break or pause.
8. n. A vacation, break from work.

GNU Webster's 1913

1. n. An opening; an aperture; a gap; a chasm; esp., a defect in a manuscript, where some part is lost or effaced; a space where something is wanting; a break.
2. n. The concurrence of two vowels in two successive words or syllables.

WordNet 3.0

1. n. a missing piece (as a gap in a manuscript)
2. n. an interruption in the intensity or amount of something
3. n. a natural opening or perforation through a bone or a membranous structure