a type of relationship in which at least one party concerned (a) has little or no real romantic interest in the cooperating party (b), but engages in a relationship for emotional and/or physical fulfilment, financial security, etc., with the hope of finding someone they genuinely wish to be with in the mean time.
it is possible for the cooperating party (b) to be aware of in-fill relationship status and continue in relationship. however, most instances of such are due to a total lack of dignity as well as a willingness to accept whatever conditions and requisites said relationship has, regardless.
it is also possible, however rare, to be involved in a double in-fill relationship. this is not to be confused with a fuck buddy. whereas an in-fill relationship not only has all of the appearances, but does in fact exercise, the majority of activities of a real relationship.
"dude, i think jen totally just used me as an in-fill relationship..."
"looked real to me."
"it sure felt real..."