pennate
adjective
pen·nate ˈpe-ˌnāt 
: of, relating to, or being usually elongate bilaterally symmetrical diatoms of an order (Pennales) having a raphe or a similar structure
Word History
Etymology
irregular from New Latin Pennales
First Known Use
1938, in the meaning defined above
Medical Definition
pennate
adjective
pen·nate ˈpen-ˌāt
: having a structure like that of a feather
especially : being a muscle in which fibers extend obliquely from either side of a central tendon