rocker

noun

1. A curved piece of wood attached to the bottom of a rocking chair or cradle that enables it to rock back and forth.

   “The cradle-rockers had done hard duty for so many years, under the weight of so many children, on that flagstone floor, that they were worn nearly flat, in consequence of which a huge jerk accompanied each swing of the cot, flinging the baby from side to side like a weaver's shuttle, as Mrs Durbeyfield, excited by her song, trod the rocker with all the spring that was left in her after a long day's seething in the suds.”

   “"By Jove, old boy," said Cripps, assisting the curate up, "should have warned you about that chair - the infernal rockers are sawn off short, you know."”

2. A rocking chair.

   “A few days before he turned 80 He was sittin' out back in a rocker”

3. The lengthwise curvature of a surfboard. (More rocker is a more curved board.)

   “All modern surfboards share a similar rocker design — Bruce Jones https://web.archive.org/web/20051212041317/http://www.brucejones.com/longboar.htm”

4. The breve below as in ḫ.

   “Like the editors of other Elamite texts, I omit the diacritic rocker from h in Elamite and from H in logograms in Elamite texts. I retain the rocker in ḫ and Ḫ in Sumerian and Akkadian.”

   “Although the exact sound value of s remains uncertain, and there is only one such sibiliant in Hittite, it is traditionally transliterated with a so-called haček: š. This should not be taken, however, as evidence that it was a palatal sound (as sh in show). The same is true for the traditional “rocker” under the laryngeal ḫ: there is no other h-sign, and the diacritic is not strictly necessary.”

   “Semitistic transliteration systems […] a number of features are common to most of them: […] ḫ (“h” with a “rocker,” conventionally called “hooked h”) for the voiceless velar/uvular fricative, IPA [x]/[χ], […]”

5. Someone passionate about rock music.
6. A musician who plays rock music.
7. (informal)A rock music song.

   “"Girls & Boys" is […] also a tart, sneering rocker, full of ingenious musical gestures […]”

8. One who rocks something.

   “It was I Sir (ſaid the Rocker) who had the honour (ſome thirty years ſince) to attend on your Highneſs in your Infancie, […]”

9. (UK)A member of a British subculture of the 1960s, opposed to the mods, who dressed in black leather and were interested in 1950s music.
10. Any implement or machine working with a rocking motion, such as a trough mounted on rockers for separating gold dust from gravel, etc., by agitation in water.
11. A tool with small teeth that roughens a metal plate to produce tonality in mezzotints.
12. A rocking horse.
13. A rocker board.
14. A skate with a curved blade, somewhat resembling in shape the rocker of a cradle.
15. A kind of electrical switch with a spring-loaded actuator.
16. A rock shaft.
17. A curved line accompanying the chevrons that denote rank, qualifying the rank with a grade.

    “Cadet Sergeant First Class: 3 Chevrons and 2 rockers. Cadet Master Sergeant: 3 Chevrons and 3 rockers. Cadet First Sergeant: 3 Chevrons, 3 rockers with a diamond inset.”