adj. — informal, slang
dim-witted or lazy.
Type: 2. Preservation — Dozy is a preservation from British English, where it is used colloquially to describe someone who is slow-witted. The OED-3 (s.v. "dozy"(1a)) lists "doze" as the adjective's origin, an obsolete transitive verb meaning 'to bewilder, confuse, perplex' that dates back to the early 1600s. Due to the surge of immigrants from the British Isles around the mid-19th century, the informal term was likely orally transferred into local vocabulary, appearing in the print record early on (see the 1852 quotation).
See also COD-2, s.v. "dozy"(2), which is marked "Brit. & Cdn informal". Not found in the American dictionaries DARE, DAE, DA, HDAS or AHD-5.