acerbus -a -um

1. 1

   harsh, bitter, unripe, sour, premature, not yet marriageable

   = asper= ācer= frāctus

2. 2

   sharp, severe, bitter (i.e., extremely painful)

3. 3

   rough, violent, severe, grievous, bitter

   = trux= ferōx= atrōx= violēns= immānis= efferus= ferus= crūdēlis= barbaricus= silvāticus= ācer= sevērus ↔ mītis↔ tranquillus↔ misericors↔ placidus↔ quietus↔ clemens

4. 4

   oppressive, distressing, sad