When looking for synonyms for the phrase "in groups", there are various options depending on the context of the sentence. Some options include "collectively", "jointly", "together", "unitedly", "as a team", "as a unit", "in collaboration", "in alliance", "cooperatively", "in partnership", "working in tandem", "simultaneously" and "concurrently". Each of these synonyms has its own nuance and implication to convey a slightly different sense of group dynamics or collaboration. The right choice of synonym will depend on the context of the sentence and the intended tone of the message being expressed.