The decade of the 1980s. / Temperatures from 80 to 89 degrees.

(Canada, US) A toll-free number or a long-distance telephone numbers; using any of North American toll-free area codes 800, 888, 877, 866, 855, 844 or 833.

(inorganic chemistry) A saturated solution of ammonia in water; ammonium hydroxide 28% (w/w as ammonia).

(Canada, US) A toll-free telephone number.

(computing, slang, derogatory) A TRS-80 microcomputer.

plural of Trash-80

(physics) A radioactive isotope, ⁸⁵₃₆Kr, having thirty-six protons and forty-nine neutrons

(idiomatic) An entity that dominates its environment. / (idiomatic) Something dangerous, menacing, or frightening that is obvious but not addressed.

plural of 800 number