so to speak

Phrased like this, in a manner of speaking, as in He was, so to speak, the head of the family, although he was only related by marriage to most of the family members. This term originally meant "in the vernacular" or "lower-class language" and was used as an aristocrat's apology for stooping to such use. [Early 1800s] Also see as it were.

The adverb has 2 meanings:

Meaning #1: as if it were really so
  Synonym: as it were

Meaning #2: in a manner of speaking
  Synonym: as we say