STEP Hebrew Lexicon: מָרַר

1) to be bitter

1a) (Qal) to be bitter

1b) (Piel)

1b1) to show bitterness

1b2) to make bitter

1c) (Hiphil) to make bitter, embitter

1d) (Hithpalpel)

1d1) to embitter oneself

1d2) to be enraged

2) (TWOT) to be strong, strengthen