1. The upper chamber of each half of the heart
   - atrium of the heart

Type of: atrium

• backside
• backslap
• backslapper
• backslash
• backslide
• backslider
• backsliding
• backspace
• backspace character
• backspace key
• backspacer
• backspin
• backstabber
• backstage
• backstair
• backstairs
• backstay
• backstitch
• backstop
• backstory
• backstroke
• backstroker
• backswept
• backswimmer
• backswing