What is the origin of 'sleep tight'?
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Definition of progymnosperm in US English:
progymnosperm
noun
BotanyOriginally: a primitive or ancestral gymnosperm. Now: specifically any of a group of sporogenous fossil plants having secondary wood resembling that of gymnosperms.
Origin
Late 19th century; earliest use found in Nature: a weekly journal of science. From pro- + gymnosperm, probably after French progymnosperme.
