nag

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To annoy by constant scolding, complaining, or urging.
2. v. To torment persistently, as with anxiety or pain.
3. v. To scold, complain, or find fault constantly: nagging at the children.
4. v. To be a constant source of anxiety or annoyance: The half-remembered quotation nagged at my mind.
5. n. One who nags.
6. n. A horse, especially:
7. n. An old or worn-out horse.
8. n. Slang A racehorse.
9. n. Archaic A small saddle horse or pony.

Century Dictionary and Cyclopedia

1. To nick; chip; slit.
2. To irritate or annoy with continued scolding, petty faultfinding, or urging; pester with continual complaints; torment; worry.
3. To scold pertinaciously; find fault constantly.
4. n. A nick; a notch.
5. n. A horse, especially a poor or small horse.
6. n. A worthless person; as applied to a woman, a jade.
7. n. A wooden ball used in the game of shinty or hockey.

Wiktionary

1. n. A small horse; a pony.
2. n. An old useless horse.
3. n. One who nags.
4. v. To repeatedly remind or complain to someone in an annoying way, often about insignificant matters.
5. v. To act inappropriately in the eyes of peers, to backstab, to verbally abuse.
6. v. To bother with persistent memories.
7. v. Other sorts of persistent annoyance, e.g.:

GNU Webster's 1913

1. n. A small horse; a pony; hence, any horse, especially one that is of inferior breeding or useless.
2. n. A paramour; -- in contempt.
3. v. To tease in a petty way; to scold habitually; to annoy; to fret pertinaciously.
4. n. A person who nags, especially habitually; called also nagger.

WordNet 3.0

1. v. remind or urge constantly
2. n. someone (especially a woman) who annoys people by constantly finding fault
3. n. an old or over-worked horse
4. v. bother persistently with trivial complaints
5. v. worry persistently