Translation:There are a lot of boys.
If anyone is wondering why you get "ohioi" when you translate "おおぜい'' (into Google Translate) is because it's correctly spelt in Kanji as "大勢" . However I'm not sure do I pronounce it as "oozei" or "taisei" . Whenever I go onto google translate it says 大勢 as "taisei". So which do I pronounce it as?
It's not a verb, the verb here is います, as in "there is". 大勢 (おおぜい) means "lots of (people)", as you can see, 大 is the same kanji as in "big", and 勢 means "groups engaged in some activity", so from that you can get the meaning. If you ever have another doubt like this, try searching for it on a dictionary, like jisho.org , I find it very useful