Entry 2 senses Webster, 1913 Muggy /(mŭg"gy̆)/ · Mug·gy · IPA /ˈmʌɡi/ 01 a. Moist; damp; moldy; as, muggy straw. 1. Moist; damp; moldy; as, muggy straw. 2. Warm, damp, and windless; uncomfortably hot and humid; sultry; as, muggy air, weather.