Prickle: A small, sharp outgrowth of the epidermis or bark.*
A prickle is a distinct botanical structure, different from a spine or a thorn. Despite the saying, every rose doesn’t have its thorn. Technically, roses have prickles like the ones pictured above.
*Harris, J.G., Harris, M.W. (2001). Plant identification terminology: An illustrated glossary (2nd ed.). Spring Lake: Spring Lake Publishing.