noun
host; toastmaster
Refers to the person who acts as the host or master of ceremonies at a gathering, party, or formal event, often responsible for welcoming guests and leading toasts.
彼がパーティーの主人役を務めた。
He acted as the host of the party.
結婚式では、友人が主人役として乾杯の音頭を取った。
At the wedding, a friend served as toastmaster and led the toast.
Compound of 主人 (host, master) and 役 (role, duty). The exact historical derivation is uncertain, but the word transparently means 'the role of a host'.