all daimyo; the feudal lords
Historical term referring collectively to the daimyo (feudal lords) of Japan, especially in the Edo period. Literally 'three hundred lords', though the number is not exact.
All the daimyo gathered in Edo for the sankin kōtai.
This policy provoked opposition from the feudal lords.
大名 is the standard term for a single daimyo; 三百諸侯 is a collective historical expression for all daimyo.
From 三百 (three hundred) + 諸侯 (lords). The number 'three hundred' is a conventional figure for the many daimyo domains, not an exact count.