Strong's G4089 — πικρός (adjective)
pikros (pik-ros') adj.
1. acrid, bitter
2. (by implication) poisonous (bodily or spiritually)
{literally or figuratively}
[perhaps from G4078 (through the idea of piercing)]
KJV: bitter 
Root(s): G4078 
Hebrew root: πήγνυμι
Occurrences: 2