The crossword solution for the term 'REALLY, INFORMALLY' is UBER, which is a four-letter word. UBER is an American international transportation network company that was founded in 2009 and is based in San Francisco, California. The company operates in over 600 cities worldwide and provides services such as ride-hailing, food delivery, package delivery, couriers, freight transportation, and electric scooter rental. UBER is often used as an informal way to say 'REALLY' or 'VERY' and is commonly used in casual conversations.