dot 1 
(dŏt)
(dŏt)n.
1.
a. A tiny round mark made by or as if by a pointed instrument; a spot.
b. Such a mark used in orthography, as above an i.
c. The basic unit of composition for an image produced by a device that prints text or graphics on paper: a resolution of 900 dots per inch.
2. A tiny amount.
3. In Morse and similar codes, the short sound or signal used in combination with the dash and silent intervals to represent letters, numbers, or punctuation.
4. Mathematics
a. A decimal point.
b. A symbol (·) indicating multiplication, as in 2 · 4 = 8.
5. Music A mark after a note indicating an increase in time value by half.
6. Computers A period, as used as in URLs and email addresses, to separate strings of words, as in www.hmhco.com.
v. dot·ted, dot·ting, dots
v.tr.
1. To mark with a dot.
2. To form or make with dots.
3. To cover with or as if with dots: "Campfires, like red, peculiar blossoms, dotted the night" (Stephen Crane).
v.intr.
Idioms: To make a dot.
dot (one's) i's
To be thorough or painstaking in attending to details.
on/at the dot
Exactly at the appointed time; punctual or punctually: arrived at nine o'clock on the dot.
[Middle English *dot, from Old English dott, head of a boil.]
dotter n.