neck guard

Short definition from Wiktionary

Noun

1. 1
   A piece of armor or protective equipment which protects the neck.
2. 2
   A piece of armor or protective equipment which protects the neck: A part of a helmet (of mail, plate, etc) which extends down to protect the neck.
3. 3
   A piece of armor or protective equipment which protects the neck: A ridge or an additional plate on a shoulder piece which projects upward to protect the neck: see passguard.
4. 4
   Alternative form of neck guard.