It should mean an outlet for an electric connection which can besited in an open position with no shelter from the weather, andwhich can safely continue to provide power with the plug insertedin bad weather (rain,wind). These are essential on open sites likecaravan sites, and in large gardens where you can't plug in insidethe house. The degree of weatherproofing may vary somewhat, andthere should always be provided fast acting earth leakage andovercurrent protection on the supply either before the outlet orincorporated in it.