2. Adjective. (context: of friends, etc.) Dependable only in the absence of trouble. ¹
¹ Source: wiktionary.com
Medical Definition of Fair-weather
1. 1. Made or done in pleasant weather, or in circumstances involving but little exposure or sacrifice; as, a fair-weather voyage. 2. Appearing only when times or circumstances are prosperous; as, a fair-weather friend. Fair-weather sailor, a make-believe or inexperienced sailor; the nautical equivalent of carpet knight. Source: Websters Dictionary (01 Mar 1998)