A timorous person is timid or shy, like your timorous friend who likes to hang out with close pals but gets nervous around big groups of new people.
The adjective timorous is actually the Latin word for ”fearful.” But timorous is a specific kind of fearfulness — the kind that strikes people before giving a speech, or walking into a crowded place where people are socializing. Also called "shy" or "timid," timorous people often become more comfortable when they see a familiar face in the crowd.