thermometers Definition

an instrument for determining temperature; especially : one consisting of a glass bulb attached to a fine tube of glass with a numbered scale and containing a liquid (such as mercury or colored alcohol) that is sealed in and rises and falls with changes of temperature

a thermometer for measuring body temperature that has a constriction in the tube above the bulb preventing movement of the column of liquid downward once it has reached its maximum temperature so that it continues to indicate the maximum temperature until the liquid is shaken back down into the bulb