mainframe
/MAYN-fraym/ · noun · Hacker Culture · Origin: 1952
Definitions
A large, powerful computer designed for high-volume transaction processing, massive I/O throughput, and extreme reliability. Despite predictions of obsolescence, mainframes still process roughly 90% of global credit card transactions and most airline reservation systems, running COBOL code sometimes older than the operators.
In plain English: A very large, very reliable computer used by banks and big companies — they've been 'dying' for 40 years but still run most of the world's financial transactions.
Example: The bank's core ledger still runs on a mainframe from the 90s, and the two people who understand the COBOL code are both approaching retirement.