pp. Sleeping with your eyes open.
1996
Didn’t he notice that half the room was glazing by the second session?
1996 (earliest)
Glazing — Corporate-speak for sleeping with your eyes open. A popular pastime at conferences and early-morning meetings.
Also:
I thank thee for the generous tear
This glazing eye could never shed.
—Lord Byron, "The Giaour: A Fragment of a Turkish Tale"