tranquillise
tran-quil-lise
verb
To make a person or animal calm or less anxious, often with medication.
"The vet will tranquillise the anxious dog."
Thesaurus
Synonyms: tranquillize, tranquilize, calm down, still, lull, quiet, calm, quieten, sedate
Antonyms: agitate, arouse, brace, charge, charge up, commove, energise, energize, excite, perk up, rouse, stimulate