Source : Webster's Revised Unabridged Dictionary (1913)

Tattoo \Tat*too"\, n.; pl. {Tattoos}.
   An indelible mark or figure made by puncturing the skin and
   introducing some pigment into the punctures; -- a mode of
   ornamentation practiced by various barbarous races, both in
   ancient and modern times, and also by some among civilized
   nations, especially by sailors.