General synonyms:
* In practice
* In reality
* Actually
* Effectively
* In effect
* Practically
* Essentially
* For all intents and purposes
* In fact
More specific synonyms, depending on context:
* Informal (when referring to something not officially recognized)
* Unofficial
* Informal
* Unacknowledged
* De jure (meaning "by right" or "legally" - used in contrast to de facto)
Example sentences:
* De facto: "While they weren't married, they lived together as a de facto couple."
* In practice: "The new rules were designed to increase efficiency, but in practice they have caused more problems."
* Actually: "He said he was going to help, but actually he just sat there watching."
* Unofficial: "The group was an unofficial support network for refugees."
The best synonym to use will depend on the specific meaning you are trying to convey.