with soul, creativity, or love -- when you put "something of yourself" into what you're doing, whatever it may be. Meraki is often used to describe cooking or preparing a meal.
(spanish) duende [dwen-day] (adjective)
This wonderful word captures an entire world of passion, energy, and artistic excellence and describes a climactic show of spirit in a performance or work of art. Duende originally meant "imp" or "goblin" and came to mean anything magical. It now has a depth and complexity of meaning that crosses artistic borders, from flamenco dancing to bullfighting. The Spanish poet Garcia Lorca wrote an eloquent essay on duende that explores the complex and inspirational flavor of its sense, and I know no better introduction.
(french) esprit de I'escalier [es-pree de less-ka/-iay] (idiom)
A witty remark that occurs to you too late, literally on the way down the stairs. The Oxford Dictionary of Quotations defines esprit de l'escalier as, "An untranslatable phrase, the meaning of which is that one only thinks on one's way downstairs of the smart retort one might have made in the drawing room."
my favorite untranslatable words; stolen from an old NPR morning edition segment.