Definition of "roach"

roach¹

/ɹəʊtʃ/

noun
plural roach
1. Certain members of the fish family Cyprinidae, including:
  1. Any fish of species in the genus Rutilus, especially:
    A common roach (Rutilus rutilus)
  2. A California roach, of the monotypic genus Hesperoleucus

roach²

/ɹəʊtʃ/

noun
plural roaches
1. (US) A cockroach.
2. (US, slang, smoking) The butt of a marijuana cigarette.
3. (US, slang, smoking) An entire marijuana cigarette, blunt, or joint.
  Quotations
  In his half hour of free time between brooms it was Willie's custom to smoke his lunch in an alleyway. He'd take just half a roach, only enough to make him feel a new day was starting, no more no less.
  1957, Alfred Maund, The Big Boxcar, Urbana: University of Illinois Press, page 106
4. (UK, slang, smoking) The filter of a rolled cigarette or joint, made from card or paper.
  Quotations
  Last toke is the yellowing fabric of the roach, containing the stuff that is less than tobacco.
  2000, Zadie Smith, White Teeth, London: Penguin Books, published 2001, page 292

roach³

/ɹəʊtʃ/

noun
plural roaches
1. (nautical) Sail material that forms a concave curve rather than straight leech (aft edge) of a sail to increase the sail area over that of a simple triangular sail.
2. A haircut or a similar-looking kind of headdress worn by some of the indigenous peoples of North America, often red.
verb
third-person singular simple present roaches, present participle roaching, simple past and past participle roached
1. (transitive) To cut or shave off the mane of a horse so that the remaining hair stands up on the neck.
2. (transitive, by extension) To cut a person's hair so that it stands straight up.

roach⁴

/ɹəʊtʃ/

noun
plural roaches
1. (UK, obsolete, mining) A bed or stratum of some mineral.
  Quotations
  After long Working of this Coal, it was found upon the rising Grounds, that there lay another Roach of Coal, at the Depth of 14 Yards under it
  1749, Rog. Mostyn, “Mineralogy”, in Philosophical Transactions and Collections to the End of the Year, volume II, London: Royal Society, page 379
2. (UK, regional) Gritty or coarse rock; especially Portland stone or similar limestone.
  Quotations
  The roach, both of the top and bottom beds, is always imperceptibly incorporated with the freestone, which is invariable situated beneath it.
  1841, C.H. Smith, “Lithology; or Observations on Stone for Building”, in The Surveyor, Engineer, and Architect, page 13