Longman Dictionary of Contemporary English
Wiktionary
n. A publicly traded limited liability company in the United Kingdom and some other jurisdictions.
Wikipedia
A public limited company (legally abbreviated to plc) is a type of public company (publicly held company) under United Kingdom company law, some Commonwealth jurisdictions, and the Republic of Ireland. It is a limited (liability) company whose shares may be freely sold and traded to the public (although a plc may also be privately held, often by another plc), with a minimum share capital of £50,000 and the letters PLC after its name. Similar companies in the United States are called publicly traded companies.
A PLC can be either an unlisted or listed company on the stock exchanges. In the United Kingdom, a public limited company usually must include the words "public limited company" or the abbreviation "PLC" or "plc" at the end and as part of the legal company name. Welsh companies may instead choose to end their names with ccc, an abbreviation for cwmni cyfyngedig cyhoeddus. However, some public limited companies (mostly nationalised concerns) incorporated under special legislation are exempted from bearing any of the identifying suffixes. The term "public limited company" and the "PLC"/"plc" suffix were introduced in 1981; prior to this, all limited companies bore the suffix "Limited" ("Ltd"), which is still used by private limited companies.