Meaning: Lissome describes people or things that are slender, flexible, light, and graceful.
Example: She was of medium stature, slender and lissome.
Synonyms: Agile, Flexible, Athletic, Limber
Antonyms: Portly, Beefy

Meaning: Something that is fleeting or short-lived is ephemeral.
Anything that is short-lived, as an insect that lives only for a day in its winged form.
Example: The film is well-directed, and its success will be more than ephemeral.
Synonyms: Fleeting, Short-Lived, Brief, Temporary
Antonyms: Enduring, Lasting, Long-Lived, Permanent

Meaning: 1. Completely contrary to nature, reason or common sense
2. Utterly foolish
Example: To a vegetarian, the idea of eating a chicken burger would seem preposterous.
Synonyms: Insane, Absurd, Crazy, Foolish, Irrational
Antonyms: Balanced, Credible, Believable, Logical

Meaning: If something is drastically reduced or killed, especially in number, you can say it was decimated
Example: The population was decimated by the chronic disease.
Synonyms: Annihilate, Exterminate, Slaughter
Antonyms: Build, Create, Bear