Delay, procrastinate, lag, loiter, dawdle mean to move or act slowly so that progress is hindered or work remains undone or unfinished.
Delay (for transitive sense see DELAY 1) usually carries an implication of putting off something (as departure, initiation of an action or activity, or accomplishment of necessary work).
Procrastinate implies blameworthy or inexcusable delay usually resulting from laziness, indifference, hesitation, or the habit of putting off until tomorrow what should be done today.
Lag implies a failure to maintain a speed or pace, either one set by and therefore in comparison with that of another or one requisite to some end or goal.
Loiter implies delay while in progress, commonly while one is walking but sometimes while one is trying to accomplish a piece of work; it also suggests lingering or aimless sauntering or lagging behind.
Dawdle carries a slighter implication of delay in progress (especially in walking) than loiter but an even stronger connotation of idleness, aimlessness, or of a wandering mind; consequently it usually implies a wasting of time or a taking of more time than is warranted.