Words: solidus [MW]

(I've always known the slash in "and/or" as the virgule, but it's also known as the diagonal and the solidus.)

Main Entry: sol·i·dus
Pronunciation: 'sä-l&-d&s
Function: noun
Inflected Form(s): plural sol·i·di /-l&-"dI, -"dE/
Etymology: Middle English, from Late Latin, from Latin, solid
1 : an ancient Roman gold coin introduced by Constantine and used to the fall of the Byzantine Empire
2 [Medieval Latin, shilling, from Late Latin; from its use as a symbol for shillings] : DIAGONAL 3