If you mean, you have a monitor that can do HD (as in HD gaming), that is a fairly flexible term as "HD" has been the norm for the last half and full-decade. Generally HD refers to 1600x1200 (or the equivalent widescreen) or higher (although some might argue high def really should be 1920x1200 or higher). XHD is generally reserved for 2048x1536 or higher.
Naturally this only counts on single display (not to be confused with single monitor/lcd) configurations.
Well if you are using it as a television, then if you looked at the link i gave for TVs, you'd compare it against these
Otherwise, it would classify as HD if you consider the widescreen version of 1600x1200 as HD (as I noted originally). Mer, personally, I dont consider that HD. But that my opinion