Jisho

It's the 可能形 of the verb 取り戻す and as such already included in the dictionary. If you want to edit a dictionary entry, just click on the "Edit in JMdict" link next to the entry and make a suggestion in the source database. If it gets accepted, then Jisho.org will also display the updated entry after a short while.
If at any point you find a word that is actually not in the database, then new JMdict entries can be created here: http://www.edrdg.org/jmdictdb/cgi-bin/edform.py?svc=jmdict&sid=

Also, a personal suggestion from me would be for you to use actually authored Japanese dictionaries instead of Google Translate if you want to double-check something. You can find the following entries for 取り戻す in...
* グランドコンサイス和英辞典: get [take] back; recover; restore
* ウィズダム和英辞典: regain; (取り返す) get* … back; (回復する) recover; (元に戻す) restore /ristɔ́ːr/.
* コンサイスEX和英辞典: get [take] back; recover; restore
* デイリーコンサイス和英辞典: (this dictionary just refers you to 取り返す, which has the following entry) take back； recover； restore； retrieve； catch up ((with one's work in English))； make up ((for lost time)).

While no dictionary is perfect, it's better than trusting Google Translate (even if it improved a lot, and of course "recoup" is not wrong I guess.) But if you feed it with just the word, it doesn't really tell you that it is already conjugated. If for example you put in a whole sentence like 私は若さが取り戻せる then it's correctly translate that as "I can regain youth".

jakobd2, thank you very much for all that information! Very useful.