in·del·i·ble 
(ĭn-dĕlə-bəl)
(ĭn-dĕlə-bəl)adj.
1. Impossible to remove, erase, or wash away; permanent: indelible ink.
2. Making a mark not easily erased or washed away: an indelible pen for labeling clothing.
3. Unable to be forgotten; memorable: an indelible memory.
[Alteration of earlier indeleble, from Latin indēlēbilis : in-, not; see IN-1 + dēlēbilis, capable of being effaced (from dēlēre, to wipe out).]
in·del′i·bili·ty n.
in·deli·bly adv.