Subsist vs Undefined - What's the difference?

As a verb subsist

is to survive on a minimum of resources.

lacking a definition or value.

(en verb)

To survive on a minimum of resources.

* Atterbury

to subsist on other men's charity

(mostly, philosophy) To have ontological reality; to exist.

* Alexander Pope

And makes what happiness we justly call, / Subsist not in the good of one, but all.

To continue; to retain a certain state.

* Milton

Firm we subsist , yet possible to swerve.

(English Citations of "subsist")

* *

(wikipedia undefined) (-)

Lacking a definition or value.

(mathematics, computing) That does not have a meaning and is thus not assigned an interpretation.

The result of division by zero is undefined .

* defined