To acclimate or become acclimated.
To adapt for comfort in extreme climates, especially as regards to temperature.
To strengthen.
To become or make (a person or thing) resistant or less sensitive.
To become or make (a consonant) more fortis; to (cause to) undergo fortition.
To make something hard or harder (tough, resistant to pressure).
To modify (a website or other system) to make it resistant to malicious attacks.
To unpalatalize or velarize.
To become hard (tough, resistant to pressure).