transverse section; cross section
Technical term used in biology, medicine, and materials science for a slice or section cut perpendicular to the long axis.
We observed a transverse section of the stem under the microscope.
縦断切片 is a longitudinal section, cut parallel to the long axis, while 横断切片 is a transverse section.
Compound of 横断 (transverse) + 切片 (section, slice). The reading せっぺん for 切片 is a technical term.