Webster's Revised Unabridged Dictionary · 1913

Bitterness

Bitterness ({not transcribed}) , noun

[Anglo-Saxon biternys; biter better + -nys = -ness.]

1.
The quality or state of being bitter, sharp, or acrid, in either a literal or figurative sense; implacableness; resentfulness; severity; keenness of reproach or sarcasm; deep distress, grief, or vexation of mind.
The lip that curls with bitterness. — Percival
I will complain in the bitterness of my soul. — Job vii. 11
2.
A state of extreme impiety or enmity to God.
Thou art in the gall of bitterness, and in the bond of iniquity. — Acts viii. 23
3.
Dangerous error, or schism, tending to draw persons to apostasy.
Looking diligently,... lest any root of bitterness springing up trouble you. — Heb. xii. 15