To Grind

(transitive) To reduce to smaller pieces by crushing with lateral motion.
(transitive) To shape with the force of friction.
(metalworking) To remove material by rubbing with an abrasive surface.
(intransitive) To become ground, pulverized, or polished by friction.
To move with much difficulty or friction; to grate.
(sports, intransitive) To slide the flat portion of a skateboard or snowboard across an obstacle such as a railing.
(transitive) To oppress, hold down or weaken.
(slang, intransitive) To rotate the hips erotically.
(slang) To dance in a sexually suggestive way with both partners in very close proximity, often pressed against each other.
(video games, intransitive) To repeat a task a large number of times in a row to achieve a specific goal.
(transitive) To operate by turning a crank.
To produce mechanically and repetitively as if by turning a crank.
(computing, dated) To automatically format and indent code.
To instill through repetitive teaching.
(slang, Hawaii) To eat.
(intransitive, slang) To work or study hard; to hustle or drudge.
(transitive, slang) To annoy or irritate (a person); to grind one's gears.

In the sports and video game senses, the past participle and past tense form grinded is often used instead of the irregular form ground.
Historically, there also existed a past participle form grounden, but it is now archaic or obsolete.
When used to denote sexually suggestive dancing between two partners, the past participle and past tense form grinded is almost always used.