Yes, it is dead, or if not very soon will be (it might have a streak of live wood on one side somewhere, but everything shown in the photo is dead). You can either cut it now, or it will fall on its own within a few years, as ash usually gets soft and falls apart quickly once dead.
It looks like it's near a nice fence, at least. Is it leaning away from or toward anything important? Sometimes these trees will get soft and start to shed limbs and chunks, sometimes they'll break off partway up the trunk first, and sometimes the whole tree will break at the roots and fall over. They're very unpredictable and with the decay shown in your photo, it might be dangerous to cut. If you're uncertain about it, your best choices are to let it fall on its own, if it won't hurt anything, or get somebody with some experience with dead ash to cut it. There's dead ash all over the country right now due to the Emerald Ash Borer as ATH mentioned above, so lots of folks are cutting dead ash right now.
Good luck, and be safe!