Main Entry: hard·en

Pronunciation: \ˈhär-d^ən\

Function: verb

Inflected Form(s): hard·ened; hard·en·ing \ˈhärd-niŋ, ˈhär-d^ən-iŋ\

Date: 13th century

transitive verb 1 : to make hard or harder
2 : to confirm in disposition, feelings, or action; especially : to make callous <hardened his heart>
3 a : inure, toughen <harden troops> b : to inure to unfavorable environmental conditions (as cold) —often used with off <harden off seedlings before transplanting>
4 : to protect from blast, heat, or radiation (as by a thick barrier or placement underground)intransitive verb 1 : to become hard or harder
2 a : to become firm, stable, or settled b : to assume an appearance of harshness or severity <her face hardened at the thought>
3 : to become gradually acclimatized to unfavorable conditions —often used with off <plants hardened off before the first frost>