"Drift", "drift in", and "drift out" all mean mean to move slowly, or to move gradually. Examples: There weren't many people at the party at 9:00, but gradually people started drifting in. The boat ran out of gas, so it just drifted through the water. He threw a bottle off the bridge and watched it drift out to sea. The leaves drifted from the trees in autumn.

These words can have many meanings Some verb uses in addition to those given by walkabout123 He drifted through life. (Went through life in a manner that wasn't purposeful) The patient drifted in and out of consciousness. (drifting here suggests that it was involuntary)

In addition to the answer below, other meanings: The boat drifted in and out on the tide/water The boxer drifted in and out of consciousness after the fight! I hope this helps, Richard

Thank you so much for your help, gentlemen, walkabout123, Teacher Richard and DavidK