Onlookersing is a verb form of "onlooker," which means someone who watches something without participating. One synonym for "onlookersing" is "observing." Observing can be used to describe a person who is quietly watching something, without giving an opinion or taking part in it. Another synonym for "onlookersing" is "witnessing." To witness is to observe something that is happening. Some people might also use the phrase "spectating" as a synonym for "onlookersing." Spectating refers to watching a specific event, such as a sports game or a performance. All of these terms, including onlookers and spectators, are used to describe people who are watching something, but not participating in it.