Synonyms for Enclosure (same or very similar meaning)
WordNet sense 1 (a naturally enclosed space):
natural enclosure
WordNet sense 2 (something (usually a supporting document) that is enclosed in an envelope with a covering letter):
inclosure
WordNet sense 3 (the act of enclosing something inside something else):
envelopment, enclosing
From the ODE community, based on WordNet
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