The act of waiting on a very important phone call. "IN THE OLDEN DAYS" (i.e., roughly two decades ago) this act would necessitate that a person remain home, near the phone, engaged in quiet activities. While phone sitting, you would have to quickly disengage yourself from all calls other than the expected one. Even walking down to the driveway may result in missing that oh-so-very-important call, such as from a perspective employer. This annoyance has become much less common in the past twenty years thanks to caller ID, call waiting, voice mail, and cell phones.
1) "I cannot go out tonight, I put a classified ad in the newspaper and now I am phone sitting."
2) "He said he would call me back about the new job. I cannot turn my cell phone off because I am phone sitting."