The English language provides various techniques for its users to create their own words. Adding a prefix, such as un or re, or adding a suffix such as able or ness. If the result of this process is meaningful and can be used in speech or writing, I would say it is a real word.However, not every word formed by such a construction is listed in dictionaries. If the meaning, derivation and pronunciation are obvious, it doesn't need to be in the dictionaries. Lexicographers seem to follow the practice of listing these constructed words when either they have a non-obvious usage, or they are used quite frequently.So, what is Chi's policy? Probably similar to the dictionaries, but if a suggestion is made I conduct my own assessment, so that I may accept such a word even if I don't find it in any dictionary.Contrary to what people may imagine, it is not my aim to include every genuine English word. The word list has a lot of very rare words - it always has - but there are plenty of even rarer words that are not included. This is not spelt out in the explanations on the website, but it does say, "...you can use almost any English word you can think of that satisfies the above rules." (What words are permitted? on the Questions and Answers page) Note the qualification "almost".In terms of the family of Oxford dictionaries, I am not inclined to accept a word that is only found in the largest of those works, the Oxford English Dictionary (which ran to 20 volumes the last time it was printed). But the next largest work, the 2-volume Shorter Oxford English Dictionary, seems to be at about the right level of inclusiveness, so a word found in that dictionary will be given careful consideration.Turning to the original suggestion, uncosted is in the Shorter Oxford, meaning "not costed; without the cost having been determined". As yelnats said, the word has been freely thrown around during the recent Australian election. It seems to be subject to regional variation around the world. The News on the Web corpus has it most frequently used in Australia, followed by Ireland, Great Britain and New Zealand. The US has only one example in over 500 million words of text, which rounds to 0.00 words per million. Another international corpus, the Corpus of Web-Based Global English shows NZ as the most frequent user of uncosted, followed by Australia and Great Britain. Presumably Americans use some other expression to describe a proposal or plan whose cost has not been estimated, e.g. the Great Wall of Mexico.I think uncosted definitely warrants inclusion as a rare word.
