A share consolidation is the term used in the United Kingdom, Ireland, Australia, Hong Kong and other Commonwealth markets for what North American markets call a reverse stock split: a company replaces its existing shares with a smaller number of new shares, each representing a proportionately larger part of the company. The main entry explains the mechanics, reasons and market processing in full.
The two terms describe the same event, with small differences of emphasis. Under UK company law, a consolidation combines shares into shares of a larger nominal amount, so ten shares of 1p become one share of 10p, and it requires a resolution passed at a shareholder meeting unless the company's articles say otherwise. In the UK it is also often paired with a special dividend or other return of cash, so that the share price and per-share figures remain comparable after the payment.
Holdings that do not divide evenly produce a fractional entitlement, which is usually sold with the proceeds paid as a cash-in-lieu payment. The opposite event, a subdivision or split, is described under share split processing.