Definition of "penguin"

Here are also birds cal'd Pen-gwins (white-head in Welch) like Pigmies walking upright, their finns or wings hanging very orderly downe like sleeves […]

1638, Thomas Herbert, Some Yeares Travels, section I

This last species of penguin, or auk, seems to be the same with the alca cirrhata of Dr. Pallis, Spicileg. Zool. Fasc. v. p. 7. tab. i. & v. fig. 1–3. F.

1772 March, “Account of the Settlement of the Malouines”, in The Gentleman's and London Magazine, page 166

More than a hundred years ago, for example, was seen the last of the great wingless penguins or auks, which early writers quaintly called " wobble-birds."

1885, Journal of the American Geographical Society of New York

These productive patches, and the houses, were each surrounded by a fence, made of a prickly shrub, called the Pinguin, which propagates itself with great rapidity.

1803, Robert Charles Dallas, The History of the Maroons‎, London: Longman and Rees, Volume 1, Letter 4, p. 82

Although it is a permanent R.A.F. station (pre-war, that is), we meander about, even in the Mess, in battle dress and flying boots, sweaters, etc., much to the disgust of some of the more dignified 'penguins' […]

1942, Hermann Hagedorn, Sunward I've Climbed, page 143

Notwithstanding his elevated status as the wing’s Senior Intelligence Officer, Monty, too, was a “penguin,” equal in that respect to an armament assistant, airframe mechanic, pigeon loftsman or any of the seventy-odd ground trades listed by the Royal Canadian Air Force at the war’s end.

1994, Monty Berger, Invasions without tears: the story of Canada's top-scoring Spitfire wing in Europe during the Second World War‎, page xi

She may have been a “penguin”—an Air Force service member who didn't fly—but it sure beat being at home, as Brady had pointed out.

2015 June 1, Kate Christie, In the Company of Women‎, Bella Books

This was to be my home for three months where ground officer cadets, referred to colloquially as ‘penguins’ were trained.

2019 November 5, Derek Esp, An Adventure in Education: The Autobiography of an Accidental Career in Education‎, Troubador Publishing Ltd, page 46