'Penguin' definitions:

Definition of 'penguin'

noun

Short-legged flightless birds of cold southern especially Antarctic regions having webbed feet and wings modified as flippers

From: GCIDE

Penguin \Pen"guin\ (p[e^]n"gw[i^]n), n. [Perh. orig. the name of another bird, and fr. W. pen head + gwyn white; or perh. from a native South American name.]
1. (Zool.) Any bird of the order Impennes, or Ptilopteri. They are covered with short, thick feathers, almost scalelike on the wings, which are without true quills. They are unable to fly, but use their wings to aid in diving, in which they are very expert. See King penguin, under Jackass. [1913 Webster]
Note: Penguins are found in the south temperate and antarctic regions. The king penguins (Aptenodytes Patachonica, and Aptenodytes longirostris) are the largest; the jackass penguins (Spheniscus) and the rock hoppers (Catarractes) congregate in large numbers at their breeding grounds. [1913 Webster]
2. (Bot.) The egg-shaped fleshy fruit of a West Indian plant (Bromelia Pinguin) of the Pineapple family; also, the plant itself, which has rigid, pointed, and spiny-toothed leaves, and is used for hedges. [Written also pinguin.] [1913 Webster]
Arctic penguin (Zool.), the great auk. See Auk. [1913 Webster]