harden

verb8

1. •
   To become hard.

   • The Chief Medical Officer of London Transport believes that public opinion against smoking will harden to the point of a total bar on the Underground, as in other countries. — 1959
2. •
   To make something hard or harder.
3. •
   (figurative) To strengthen.
4. •
   (informal) To get an erection.

   • He hardened as he imagined himself running his hands over her small breasts — 1999
5. •
   To modify (a website or other system) to make it resistant to malicious attacks.
6. •
   To become or make (a person or thing) resistant or less sensitive.

   • (obs.)
7. •
   To become or make (a consonant) more fortis; to (cause to) undergo fortition.
8. •
   To unpalatalize or velarize.

   • Of course one needs to keep in mind the fact that *tʹ and *dʹ are hardened before *e and *i in Ukrainian and Rusyn[…] — 2007