great enthusiasm; very keen; in high spirits
Describes a state of being very eager, excited, or in a great mood about something. Often used when someone is really looking forward to an event or activity.
He is really excited about tomorrow's trip.
She was very enthusiastic about the new project and started preparing right away.
Compound of 大 (おお, 'big, great') + 乗り気 (のりき, 'eagerness, enthusiasm'). The exact historical derivation is uncertain, but the word transparently intensifies 乗り気.