witless

As a noun taxonomy

is the science or the technique used to make a classification.

As an adjective witless is

destitute of wit or understanding; wanting thought; hence, indiscreet; not under the guidance of judgment.

Witless is a see also of spitless.

As adjectives the difference between witless and spitless

is that witless is destitute of wit or understanding; wanting thought; hence, indiscreet; not under the guidance of judgment while spitless is having a dry mouth; greatly frightened; (see usage notes below).