commitermenship
Defined as a step above an intimate relationship and a step below formal engagement. A type of relationship in which a partner expresses the desire of commitment to develop the relationship further with intentions of marriage in the future. Most often used when too early in the relationship for public labels and formalities of engagement. The sole purpose of communicating a commitermenship would usually be personal and private directly between the individuals.
Babe, I'd like to take our relationship to the next level because I'm invested in you as a person. Let's have a commitermenship.