1. Plural of mater; mothers (chiefly British, informal or dated).
Usage: informal; chiefly British; dated
2. Plural of mater; the hard outer membrane enveloping the brain and spinal cord (medical/anatomical term).
Usage: anatomy; technical

Examples

• The school invited all the maters to the annual open day.
• In anatomy class, we studied the three layers of the meninges, including the maters.
• My friend's maters organized a surprise birthday party for us.
• The protective maters surrounding the spinal cord prevent injury.
• Several maters volunteered to help with the school fundraiser.