Verb
(law, England & Wales, Northern Ireland, idiomatic) To formally contract to purchase, sell or otherwise be party to a disposition of an estate in land; usually requiring the payment of a deposit by one of the parties.
(law, England & Wales, Northern Ireland, chiefly by legal practitioners) To create a contract for the disposition of an estate in land between negotiating parties, by a process which is immediately followed by the exchange of executed counterparts of the contract between each party's legal representative.
Source: en.wiktionary.org