grommet
grommet (grom"met) , noun
[French gourmette curb, curb chain, from gourmer to curb, thump, beat; compare Armor. gromm a curb, gromma to curb.]
1.
A ring formed by twisting on itself a single strand of an unlaid rope. Sometimes written grummet.
2.
Any eyelet or ring of metal or other material inserted in a hole in a sheet of some other material; in sailing, a metallic ring in or for a sail or a mailbag.
3.
A ring of rubber or other insulating material inserted in a hole in some surface of a device, to prevent wires passing through the hole from making contact with the surface; used especially in electrical and electronic devices, to prevent undesired electrical contact.
4.
(Military) A ring of rope used as a wad to hold a cannon ball in place.