Meaning: Lassitude is defined as a feeling of lethargy or a lack of mental or physical energy.
Example: Couch potatoes make lassitude into an art form.
Synonyms: Lethargy, Apathy, Dullness, Fatigue
Antonyms: Action, Diligence, Energy, Interest, Vigor

Meaning: Rancor is a bitter and long lasting hatred.
Example: He was filled with rancor after losing the last match.
Synonyms: Animosity, Grudge, Resentment, Bitterness
Antonyms: Friendliness, Kindness, Sympathy, Liking

Meaning: To aerate means to fill, combine or supply with oxygen or expose to fresh air.
Example: Please aerate your old sneakers right now.
Synonyms: Oxygenate, Freshen, Inflate

Meaning: Fortuitous means by chance, like a lucky accident.
Example: What a fortuitous coincidence my friend!
Synonyms: Accidental, Fortunate, Odd, Random
Antonyms: Calculated, Deliberate, Intentional, Planned

Meaning: A mendacious person is one who tells lies habitually and intentionally.
Example: If you catch someone intentionally manipulating you with a falsehood, that person is just plain mendacious.
Synonyms: Dishonest, Deceitful, Fallacious, Fraudulent
Antonyms: Frank, Honest, Truthful, Sincere