its a type of lag that makes ur tnts explode in slow motion(http://www.youtube.com/watch?v=7lSYSWF1YpI), very slow updates(ex. slow falling sand, gravel, etc.), sound(eating sound, mob sound) not working properly, and many other lags that look like server lag even though ur playing in single player survival(or creative too). this kind of lag happens only in certain maps(tested this by creating many maps and play) such as Waking Up by Vechs, possibly black desert II by vechs(not released yet but on vechs videos he shows same problem).
http://www.youtube.com/watch?v=3fi58ITZaPM&feature=g-user <- famous map maker Vechs experiencing this "lag"