The non-Sovereign partner in a reigning couple.
Definition from Kingdom Law
Typically, there is little need to specify which of a royal couple is the Sovereign and which is the Consort; they rule together as a unit. There are a few additional duties for the Sovereign and these are defined in Kingdom Law (generally, in articles concerning Crown Lists and the Crown Prince and Crown Princess).
Upon successfully completing their reign, the Consort becomes a member of either the Order of the Rose (kingdom consorts) or the Order of the Valorous Estate (principality consorts).