For a player or foursome partners to be 'dormie' in matchplay is to be as many holes up as there are holes remaining.
This means that a half at any one of the closing holes is good enough to win the match.
The word 'dormie' on its own is sufficient, but it is often expressed as 'dormie four' or 'dormie three', etc.., depending on the number of holes remaining.
'Dormie' can only apply in matches where the result is decided after 18 holes. For example, in the Ryder or Walker Cups, matches can be halved (rather than playing extra holes). However, this is not the case in the WGC Matchplay Championship, in which every match must be played until a winner emerges.
We know of two possible origins for the word, although most dictionaries simply list the etymology of 'dormie' as unknown.
The USGA Museum explains the term as being a derivation of the French word 'dormir', meaning to sleep - the theory being that since a player who is 'dormie' can no longer lose the match, they can now relax, or metaphorically 'go to sleep'.
Some purists, however, attribute this use of the word to the first known women's golfer - Mary Queen of Scots. She spent much of her childhood in France and spoke the language fluently. She is also credited by some with bringing the word 'caddie' from France to Scotland.
Keen matchplay golfers will of course tell you that the quickest way to lose a good lead is to relax...
Staying in Scotland, but with no evidence before the late 18th and early 19th century, another theory holds that it is local Scottish slang for 'dormice'.
Dormice were at home on the heaths and near the coasts where golf was played. As the dormice were extremely shy and would usually hide at the approach of golfers, it was considered a good omen to see one. An 1828 essay by Sir Walter Scott about a visit to Carnoustie refers to the habit of local 'gowfers' who spattered their conversation with the names of small rodents during matches.
The word 'dormy' or 'dormie' is also found in use at golf clubs which have a 'Dormy House', but in this context it simply means somewhere for visiting golfers to sleep overnight.