1. Elegiac ADJECTIVE having a mournful quality:
"the song is a somber effort, elegiac
in its approach"

2. Apprise ( verb )to give notice to Synonym - inform, advise
Antonym – devalue, depreciate

3. Loquacious Adjective tending to talk a great deal; talkative.
Synonym – chatty, garrulous
Antonym – reticent, taciturn
The math teacher across the hall is loquacious, he talks all period.
Loquacious

4. implacable ( adjective )not to be appeased, mollified, or pacified
Synonym – unforgiving, unsparing
Antonym - appeasable
implacable

5. Sardonic ADJECTIVE disdainfully or skeptically humorous : derisively mocking, satirical “SNL satirical skits are known for their sardonic wit"