Dictionary entry

πικραίνω

G. Abbott-Smith's A Manual Greek Lexicon of the New Testament

πικραίνω

(< πικρός), [in LXX for מרר, קצף, etc.;]

to make bitter: Re 10:9; pass., Re 8:1110:10; metaph., to embitter (LXX): pass., seq. πρός, Col 3:19.†