R thə(r)ˈmäməd.ər, -ämətər, - R thəˈmäməd.ə(r, -ämətə(r noun
Etymology: French thermomètre, from Greek thermē heat + French -o- + -mètre -meter — more at therm
1. : an instrument for determining temperature usually by means of a scale graduated directly in temperature units and consisting typically of (1) a device having a bimetallic element whose expansion or contraction indicates a change in temperature or (2) a glass bulb attached to a fine tube of glass with a numbered scale etched on or fastened to it and containing a liquid (as mercury or colored alcohol) that is sealed in and rises and falls with changes of temperature and that indicates the temperature by the number corresponding to the top of the column of liquid — see dry-bulb thermometer , gas thermometer , resistance thermometer , reversing thermometer , wet-bulb thermometer
2. : one that serves as a precise indicator of a position on a scale
retail sales as a business thermometer
letters to the editor — a thermometer of public opinion