Sunny/ˈsʌni/ Definition 1 of 2Pro Tip 1/3Weather Specific Use 'sunny' to describe weather conditions, not indoor brightness. We'll go to the park since it's sunny. Pro Tip 2/3Positive Vibe 'Sunny' often implies a positive, pleasant day suitable for outdoor activities. Let's plan our picnic for a sunny afternoon. Pro Tip 3/3Natural Light 'Sunny' indicates natural sunlight, not artificial light sources. She opened the curtains to let the room be sunny.