noun
marriage between coworkers
Refers to two employees of the same company getting married. Often implies that one of them may leave the company afterward, especially in traditional Japanese corporate culture.
彼らは社内結婚して、今も同じ会社で働いている。
They had a workplace marriage and still work at the same company.
職場結婚 is a broader term for marriage between people who work at the same workplace, not necessarily the same company. 社内結婚 specifically refers to marriage within the same company.
Compound of 社内 (within the company) and 結婚 (marriage).