homothallic

is likely misspelled.

has no English definition.

As an adjective homothallic

is producing male and female reproductive structures in the same plant.

As a noun taxonomy

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

As an adjective homothallic is

(of some algae and fungi) producing male and female reproductive structures in the same plant.

As adjectives the difference between bisexual and homothallic

is that bisexual is sexually attracted to members of two or more genders while homothallic is producing male and female reproductive structures in the same plant.

As a noun bisexual

is a person who is bisexual. Someone who is attracted to people of two or more genders.