di·al 
(dīəl, dīl)
(dīəl, dīl)n.
1. A graduated surface or face on which a measurement, such as speed, is indicated by a moving needle or pointer.
2.
a. The face of a clock.
b. A sundial.
3.
a. The panel or face on a radio or television receiver on which the frequencies or channels are indicated.
b. A movable control knob or other device on a radio or television receiver used to change the frequency.
4. A rotatable disk on a telephone with numbers and letters, used to signal the number to which a call is made.
v. di·aled, di·al·ing, di·als or di·alled or di·al·ling
v.tr.
1. To measure with or as if with a dial.
2. To point to, indicate, or register by means of a dial.
3. To control or select by means of a dial: dial a radio station.
4. To call (a party) on a telephone.
5. To signal (a number) in making a telephone call: The program dials the number and then connects to the file server.
v.intr.
Phrasal Verbs: 1. To use a dial.
2. To use a telephone.
dial down
Informal To reduce the intensity of: tried to dial down the controversy.
dial up
Informal To increase the intensity of: dialed up the action in the movie's sequel.
[Middle English, sundial, clock, from Old French dyal, from Medieval Latin diāle, from neuter of diālis, daily, from Latin diēs, day; see dyeu- in the Appendix of Indo-European roots.]
dial·er n.