露水夫妻

lùshuǐfūqī
a couple in a short-lived, improper relationship

CEDICT

露水一經陽光曝晒即蒸散。比喻暫時結合而非正式的夫妻。

重編國語辭典

Entry Composition

1 露水 lùshuǐ
  1. dew
  2. fig. short-lasting
  3. ephemeral
2 夫妻 fūqī husband and wife; married couple