京腔 simply means 'Beijing pronunciation'. Distinct from 普通话 - Standard Mandarin was built on the Beijing phoneme inventory but lacks the heavy erhua, swallowed syllables, and 儿化 vocabulary (胡同儿, 没门儿, 哥们儿) that mark a real 京腔 speaker.
usage
Also refers historically to a Qing-dynasty operatic style (京腔戏) that preceded Peking opera. In modern speech, almost always means 'Beijing accent' of everyday Mandarin.