Longman Dictionary of Contemporary English
marriage of convenience
noun
EXAMPLES FROM CORPUS
▪ A marriage of convenience brings danger, suspense, and love to Marianne.
▪ He told me he was in a marriage of convenience.
▪ It was a marriage of convenience.
▪ The Home Office had suspected that it was a marriage of convenience, to get the woman in.
▪ This was a highly effective marriage of convenience, helping to balance the demand for electricity.
▪ Though the diplomatic courtship is at an early stage, the Foreign Office is optimistic about such a marriage of convenience.
Wiktionary
marriage of convenience
n. A marriage motivated by some reason other than love; especially one conducted to obtain entry or residence rights in a country.
WordNet
marriage of convenience
n. a marriage for expediency rather than love
Wikipedia
Marriage of convenience
A marriage of convenience (plural marriages of convenience) is a marriage contracted for reasons other than that of relationship, family, or love. Instead, such a marriage is orchestrated for personal gain or some other sort of strategic purpose, such as political marriage. In the cases when it represents a fraud, it is called sham marriage.