goop

Etymology

1930s, perhaps a variant of goo; compare gloop.

noun

1. (informal, usually uncountable) A thick, slimy substance; goo.
   The flesh [of the mistletoe berry] is sticky, and forms strings and ribbons between my thumb and forefinger. For the mistletoe, this viscous goop – and by the way, viscous comes to English from viscum – is crucial. The stickiness means that, after eating the berries, birds often regurgitate the seeds and then wipe their bills on twigs – leading to the seeds' getting glued to the tree, where they can germinate and begin the cycle anew. 23 December 2014, Olivia Judson, “The hemiparasite season [print version: Under the hemiparasite, International New York Times, 24–25 December 2014, page 7]”, in The New York Times, archived from the original on 2014-12-23
2. (countable, informal, derogatory, dated) A silly, stupid, or boorish person.
   I pointed out that Stiffy, who is pure padded cell from the foundation up, was planning to marry the Rev. H.P. Pinker, himself as pronounced a goop as ever preached the Hivites and Hittites 1963, P.G. Wodehouse, Stiff Upper Lip, Jeeves, chapter 22

verb

1. (informal) To apply a thick, slimy, or goo-like substance.
2. (informal, possibly obsolete) To stare; gawk.
   Young John blushed at being found “gooping” at himself in the glass. 1925, Margaret Turnbull, Alabaster Lamps
   He always said vegetables are grown to be eaten, not gooped at. Even a donkey doesn't want a carrot a foot long. I've always remembered. Of course he never won a thing at the Show. 1955, Ring Up the Curtain: Four Plays
   it was dreadful, it was frightening, to be the sort of woman that, for some unknown reason, all men looked at, all men gooped at, all men—wanted. 1968, Christianna Brand, What Dread Hand: A Collection of Short Stories, The Hornet's Nest