Thick  —adj. 1 of great or specified extent between opposite surfaces. 2 (of a line etc.) Broad; not fine. 3 arranged closely; crowded together; dense. 4 (usu. Foll. By with) densely covered or filled (air thick with smoke). 5 a firm in consistency; containing much solid matter. B made of thick material (a thick coat). 6 a muddy, cloudy; impenetrable by sight. B (of one's head) suffering from a hangover, headache, etc. 7 colloq. Stupid. 8 a (of a voice) indistinct. B (of an accent) very marked. 9 colloq. Intimate, very friendly. —n. Thick part of anything. —adv. Thickly (snow was falling thick).  a bit thick colloq. Unreasonable or intolerable. In the thick of at the busiest part of. Through thick and thin under all conditions; in spite of all difficulties.  thickish adj. Thickly adv. [old english]