1. The quality of being covered with prickly thorns or spines
   "The thorniness of the cactus made it difficult to handle";
   - prickliness, bristliness, spininess, spinescence [formal]
    
2. The property of being full of difficulties, complexities, or controversial points
   "And, given the thorniness of the issues on the table, a work stoppage at all West Coast ports is not to be ruled out"
    
3. A rough and bitter manner
   "His thorniness in dealing with colleagues made him unpopular";
   - bitterness, acrimony, acerbity, jaundice, tartness

Type of: difficultness, difficulty, disagreeableness, raggedness, roughness