/ θəˈmɒmɪtə(r); NAmE θərˈmɑːm-/ noun
an instrument used for measuring the temperature of the air, a person's body, etc. :
a thermometer reading
—picture at illness
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WORD ORIGIN
mid 17th cent.: from French thermomètre or modern Latin thermometrum , from thermo- of heat + -metrum measure.