Wiktionary
double-book
vb. 1 (context transitive English) To erroneously book or reserve something for two people, when there is only space for one. 2 (context reflexive English) To erroneously make arrangements to do two things at the same time, such that it is impossible to keep both arrangements.
Usage examples of "double-book".
James, absolutely livid at being mistaken for the manager by some enraged theatregoer whose seats had been double-booked, was now trying to explain the extremely complicated plot of The Merry Widow to the viewers.
As every room within ten miles of Paradise was double-booked by reporters, he ended up at The Bell in Rutminster, an old coaching inn overlooking the River Fleet.