A large digital computer serving 100-400 users and occupying a special air-conditioned room WordNet 3.0 & Open English WordNet

A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise resource planning, and large-scale transaction processing. Wikipedia

Type of large data processing system. Wikipedia Disambiguation

Computers used primarily by large organizations for critical applications Wikidata

A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously or intensive computational tasks. OmegaWiki

A large, powerful computer able to manage very many simultaneous tasks and communicate with very many connected terminals; used by large, complex organizations (such as banks and supermarkets) where continuously sustained operation is vital. Wiktionary

Large computer. Wiktionary (translation)