an instrument, formerly much used for showing the time of day from the shadow of a style or gnomon on a graduated arc or surface; esp., a sundial; but there are lunar and astral dials. the style or gnomon is usually parallel to the earth's axis, but the dial plate may be either horizontal or vertical.-the graduated face of a timepiece, on which the time of day is shown by pointers or hands.-a miner's compass.-to measure with a dial.-to survey with a dial.