Definition of

Undecimal

A way of writing numbers using 11 digits

Uses the normal decimal digits 0 to 9 with the letter "A" used for the 11th digit:

0,1,2,3,4,5,6,7,8,9,A

Also called Base 11

Example: 2A in undecimal is equal to 32 in decimal (2×11+10=32)