WordNet (r) 3.0 (2006):
playpen n 1: a portable enclosure in which babies may be left to play [syn: playpen, pen]The Jargon File (version 4.4.7, 29 Dec 2003):
playpen n. [IBM] A room where programmers work. Compare salt mines.The Free On-line Dictionary of Computing (30 December 2018):
playpen (IBM) A room where programmers work. Compare salt mines. [Jargon File]