1 also clunker: An old, dilapidated vehicle or other mechanical device. [Prob echoic] chiefly Nth, West See Map
1938 AmSp 13.307 [Bus driver lingo], Clunk. A bus, usually old and worn-out. 1942 Berrey–Van den Bark Amer. Slang 766.3, Decrepit car. Clunk, crate of worms, . . junk heap. 1947 Jones Evergreen Land 181 WA, They had those old DC-4’s—those old four-motor Douglas clunks. 1950 WELS (Old broken-down car) 2 Infs, WI, Clunk; 2 Infs, Clunker; (Joking names for a pocket watch) 1 Inf, Clunker. 1956 AmSp 31.227 [Air Force slang], Clunker. . . An aircraft that performs poorly. 1957 AmSp 32.193 MA, NH [Among target club members], Clunker. . . An old, dilapidated, or poorly rebuilt handgun. . . Sometimes modified into old clunk. 1960 Wentworth–Flexner Slang, Clunk. . . An old or worn-out piece of machinery; an old bus or car. c1935. 1963 AmSp 38.43 RI [Truckers’ speech], Clunker [An old truck]. 1965–70 DARE (Qu. N5, . . Automobile, especially an old or broken-down car) 44 Infs, chiefly Nth, (Old) clunker; ID3, WA3, 6, 12, 30, WI34, (Old) clunk; (Qu. N6) UT5, Clunker; (Qu. O2, . . An old, clumsy boat) Infs CA80, 86, MI10, 80, 90, MA1, NH18, PA76, (Old) clunker; MN33, WI34, (Old) clunk.
2 also clunker: A hard blow.
1943 in 1960 Wentworth–Flexner Slang, Clunk. . . “One clunk on the knuckle.” 1968–70 DARE (Qu. Y11, . . “Joe really hit him a _____.”) Infs CT43, NY96, Clunker.
3 also clunkhead: A dull, stupid person; a clumsy or careless person.
1934 Runyon Blue Plate Special (DAS), Because you’ll be listed among the clunks. 1950 WELS (A very awkward or clumsy person) 2 Infs, WI, Clunk. 1952 in 1960 Wentworth–Flexner Slang 112, “Some clunkhead sent me three live quail!” Arthur Godfrey, radio, Jan. 1. 1966–68 DARE (Qu. N12, . . Somebody who drives carelessly or not well) Inf WA8, Clunk; (Qu. HH16, Uncomplimentary words . . used . . of a person: “Don’t invite him. He’s a _____.”) Inf IA46, Clunk. 1974 AmSp 49.205, (Terms for low intelligence) Clunkhead.