noun. any of the cylindrical filaments characteristically growing from the epidermis of a mammal.
noun. hairlike structure especially on the surface of a cell or microorganism.
1. Noun, singular or mass The bacterium that extends the sex pilus then copies a plasmid and passes the copy through the tube into the other bacterium. 2. Coordinating conjunction The word *pilus* (plural is pili) comes from the Latin word for hair.