The phrase "not outside" can be replaced with a number of synonyms, depending on the context. In some cases, "not inside" may be appropriate, as it conveys the opposite meaning of being indoors or contained within a space. Other options might include "not beyond," "not exceeding," or "not surpassing," which all suggest limitations or boundaries that are being respected or observed. Alternatively, "not away from" or "not apart from" could be used to convey a sense of proximity or connection to something specific. Ultimately, the choice of synonym will depend on the specific nuances of the situation at hand.