interosseus

noun

in·​ter·​os·​se·​us ˌin-tər-ˈäs-ē-əs 

plural interossei -ē-ˌī 

: any of various small muscles arising from the metacarpals and metatarsals and inserted into the bases of the first phalanges:

a

: dorsal interosseus

b

: palmar interosseus

c

: plantar interosseus