tkwait variable name
tkwait visibility name
tkwait window name
http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/tkwait.html
"Anyway, it's a little bit confusing that tkwait is 'scope-proof'. ;)" Another reminder to read the man page carefully: "If the first argument is variable (or any abbreviation of it) then the second argument is the name of a global variable and the command waits for that variable to be modified."
See also:
Tk syntax help - Arts and Crafts of Tcl-Tk Programming - Category Command