['kɑ:slgɑ:d]
n.
佃农在战时防卫城堡之义务

Castle-guard \Cas"tle-guard`\, n.
1. The guard or defense of a castle.

2. (O. Eng. Law) A tax or imposition an a dwelling within a
certain distance of a castle, for the purpose of
maintaining watch and ward in it; castle-ward.

3. A feudal tenure, obliging the tenant to perform service
within the realm, without limitation of time.