thicken

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To make or become thick or thicker: Thicken the sauce with cornstarch. The crowd thickened near the doorway.
2. v. To make or become more intense, intricate, or complex: The leader's departure thickens the problems. Our apprehension thickened.

Century Dictionary and Cyclopedia

1. To become thick or thicker. To grow dense.
2. To become deeper or heavier; gain bulk.
3. Of a liquid, to approach more nearly a state of solidity; gain firmer consistency; also, to become turbid or cloudy.
4. To become dark or obscure; specifically, of the weather, etc., to become misty or foggy.
5. To grow more intense, profound, animated, intricate, etc.; become complicated.
6. To gain in number or frequency; hence, to crowd; throng.
7. To become indistinct.
8. To make thick or thicker. To make dense, close, or compact; specifically, to full, as cloth.
9. To increase in depth, or distance between opposite surfaces; hence, figuratively, to make stouter or more substantial; strengthen.
10. Of liquids, to increase the consistency of; inspissate: as, to thicken gravy with flour; also, to render turbid or cloudy.
11. To obscure with clouds or mist; befog.
12. To make more numerous or frequent; redouble: as, to thicken blows.
13. n. A spelling of thick 'un (which see, under thick, a.).

Wiktionary

1. v. transitive To make thicker (in the sense of wider).
2. v. transitive To make thicker (in the sense of more viscous)
3. v. intransitive To become thicker (in the sense of wider).
4. v. intransitive To become thicker (in the sense of more viscous).

GNU Webster's 1913

1. v. To make thick (in any sense of the word).
2. v. To render dense; to inspissate.
3. v. To make close; to fill up interstices in.
4. v. obsolete To strengthen; to confirm.
5. v. To make more frequent.
6. v. To become thick.

WordNet 3.0

1. v. make viscous or dense
2. v. make thick or thicker
3. v. become thick or thicker