Well, probably several ways. When thinking of heaven, and the future, I think of it as a different state of matter. Like the sun, which will not be the same. If it were the same, it would 'burn out' eventually. Another part of decay might be corruption.
Lu 12:33 - Sell that ye have, and give alms; provide yourselves bags which wax not old, a treasure in the heavens that faileth not, where no thief approacheth, neither moth corrupteth. Even gold would eventually 'perish'
That perisheth. Not that gold perishes by the process of being tried in the fire, for this is not the fact, and the connexion does not demand this interpretation. The idea is, that gold, however valuable it is, is a perishable thing. It is not an enduring, imperishable, indestructible thing, like religion. It may not perish in the fire, but it will in some way, for it will not endure for ever.
http://www.studylight.org/com/bnn/view.cgi?book=1pe&chapter=1&verse=7#1Pe1_7
I figure our bodies will decay or corupt away. Radioactive decay also, that really kind of defines the state of the physical universe we are in.
The standard definitions pretty well cover it.
de·cay
(d
-k
)
v. de·cayed,
de·cay·ing,
de·cays
v.intr. 1. Biology To break down into component parts; rot.
2. Physics To disintegrate or diminish by radioactive decay.
3. Electronics To decrease gradually in magnitude. Used of voltage or current.
4. Aerospace To decrease in orbit. Used of an artificial satellite.
5. To fall into ruin:
a civilization that had begun to decay.
6. Pathology To decline in health or vigor; waste away.
7. To decline from a state of normality, excellence, or prosperity; deteriorate.