In a philosophical sense; value, cohesion.
In this sense, meaning can only be defined in a context, whether it is the meaning of an entity, an action, a statement or an event. Meaning is a defining feature of information, either information itself, information associated with something or implied information. Something is only meaningful if its information can be interpreted and understood.
DNA, for instance, carry genetic information that is only meaningful in the context of replication, longevity and reproduction. DNA doesn't have a meaning outside of this context, other than as an unusually large molecule. (In the case of DNA, the interpreter is a part of the DNA itself, reading the information encoded in the molecular structure, to make new copies of itself.)
Higher lifeforms, and especially humans, can perceive meaning in a much larger scope. Language is information and carry information, in an analogy to genes the rules for encoding and decoding meaning in language are built into the language itself. Language can carry information that pertains to anything, and thus, it is descriptive information about the environment in which the language exists. This information is also genetic and is sometimes referred to as memes, a term coined by Richard Dawkins.
Meaning is also closely related to value. Something has meaning in the sense that it has a value, e.g "This action is better than that action." This implies that each action has a value, and the value can only be determined in the context the action is performed. The meaning of the action can be derived from the value of it, if it's a "good" action or a "bad" action. The action itself, in isolation, can neither be "good" or "bad", and is thus meaningless.
Further references: hermeneutics, ethics.