1. Indicating a lack of maturity
   "infantile behaviour"
   - childish 
2. Of or relating to infants or infancy
   "infantile paralysis" 
3. Being or befitting or characteristic of an infant
   "infantile games"

See also: immature, infancy, young

• sound pressure level
• sound projection
• sound property
• sound ranging
• sound recording
• sound reflection
• sound reproduction
• sound spectrograph
• sound spectrum
• sound structure
• sound system
• sound truck
• sound unit
• sound wave
• soundable
• soundboard
• soundbox
• sounder
• sounding
• sounding board
• sounding lead
• sounding line
• sounding rocket
• soundless
• soundlessly