1. Of sound waves with frequency greater than 1000 million hertz 
2. Moving at more than five times the speed of sound

Encyclopedia: Hypersonic

• scholasticism
• scholia
• scholiast
• scholium
• Schomburgkia
• Schonbein
• school
• school assignment
• school bell
• school board
• school bus
• school crossing
• school day
• school dictionary
• school district
• school newspaper
• school of dentistry
• school of law
• school of medicine
• school of music
• school of nursing
• school of thought
• school paper
• school phobia
• school principal