v.1. To move away slowly, especially while being carried by currents of air or water: The stick drifted off with the river current. The child let go of the balloon and it drifted off toward the horizon.
2. To walk slowly toward some other place or area: As they left the cafeteria, the students started drifting off toward the gym.
3. To fall asleep gradually: I drifted off while watching television. I was so tired that I drifted off.
4. To stop listening or paying attention to someone or something: The professor noted that most of the students had drifted off during the lecture.