An "unscheduled visit" means showing up at someone's place or office without making an appointment or letting them know in advance.
Sentences with «unscheduled visit»
Having observed and as such chided the contractors for what he described as slow pace of work on site, pointing out that he would continually be paying unscheduled visit to site to ensure that contracts awarded by government are properly monitored. (nigeriapoliticsonline.com)
While it's okay to ask parents to refrain from unscheduled visits during naptime, avoid providers that frown upon unannounced visits other times of the day. (thetoddle.com)
These two fixes were our only unscheduled visits to the VW dealer. (automobilemag.com)