Not in standard ECMAScript-262 3rd ed.
Upcoming 5th edition (currently draft), on the other hand, introduces accessors in object initializers. For example:
var o = {
a:7,
get b() { return this.a + 1; },
set c(x) { this.a = x / 2; }
};
Similar syntax is already supported by Javascript 1.8.1 (as a non-standard extension of course).
Note that there are no "completed" ES5 implementations at the moment (although some are in progress)
