British spelling; not favorable, advantageous, or beneficial; expressing or showing disapproval or dislike.
British spelling of unfavorable, using the -able suffix with disfavor. The -our- spelling marks it as Commonwealth English.
Weather forecasts in Britain always contain 'disfavourable conditions' rather than 'unfavorable conditions,' and it sounds more formal and dramatic—the extra syllable makes bad news sound more official.
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