tranquillise

Verb

tranquilize (third-person singular simple present tranquilizes, present participle tranquilizing, simple past and past participle tranquilized)

1. (transitive) To calm (a person or animal) or put them to sleep using a tranquilizer dart.
   • The escaped lion was finally tracked down, tranquilized, and safely returned to the zoo.

   Synonyms:

   dart, sedate

2. (literary, transitive) To make (something or someone) tranquil.
   • […] with words of sweetest kindness and consolation, he soothed and tranquilised me.1779, Frances Burney, Evelina, Dublin: Price, Corcoran et al., Volume 2, Letter 14, p. 87

   Synonyms:

   appease, calm, pacify

3. (intransitive, obsolete, rare) To become tranquil.
   • Seest thou not, that this unseasonable gravity is admitted to quell the palpitations of this unmanageable heart? But still it will go on with its boundings. I’ll try, as I ride in my chariot, to tranquillize.1748, [Samuel Richardson], “Letter I”, in Clarissa. Or, The History of a Young Lady: […], volume V, London: […] S[amuel] Richardson; [a]nd sold by John Osborn, […], →OCLC, page 11

   Synonyms:

   calm down, relax

4. (transitive) To dart (a person or animal) with a sedative
   • The bear should go down several minutes after being tranquilized.