from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The use of one's fingers to express numbers.
from the GNU version of the Collaborative International Dictionary of English
- n. The art of numbering or counting by the fingers.
from The Century Dictionary and Cyclopedia
- n. The art of counting or numbering on the fingers.
From dactylo- + -nomy. (Wiktionary)
I especially enjoyed the the maths chapter, which includes topics like how to count to a million on your fingers I've tried dactylonomy before and how to estimate square roots in your head.