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Webster 1913 Edition
Improving
Im-prov′ing
,Adj.
 Tending to improve, beneficial; growing better. 
– Im-prov′ing-ly
, adv.
Improving lease 
(Scots Law)
, an extended lease to induce the tenant to make improvements on the premises.
 Webster 1828 Edition
Improving
IMPROV'ING
,ppr.