make or become hard or harder: [no object]:wait for the glue to harden [with object]:bricks which seem to have been hardened by firing
make or become more severe and less sympathetic: [with object]:she hardened her heart
make or become tougher and more clearly defined: [no object]:suspicion hardened into certainty [with object]:this served only to harden the resolve of the island nations
[no object] (of prices of shares, commodities, etc.) rise and remain steady at a higher level:if oil prices harden at the end of this century
inure a plant to cold by gradually increasing its exposure to it:the cuttings can be left in the frame until mid May, when they can be hardened off and planted out
