What is Stiff ?
Stiff is (adj) 1. which does not move easily The lock is very stiff – I can’t turn the key. I’ve got a stiff neck. She was feeling stiff all over after running in the race. 2. with hard bristles You need a stiff brush to get the mud off your shoes. 3. difficult He had to take a stiff test before he qualified. 4. formal, not friendly His attitude was very stiff towards her. 5. strong, not weak They face stiff competition. A stiff breeze was blowing across the bay. He got a stiff reprimand from the boss. (NOTE: stiffer – stiffest)
source: Easier English, Student Dictionary Upper Intermediate Level