People often ask what emotions/thoughts any number of specific nonverbal signals indicate. This is not always a straight forward answer. Many (but not all) body language signs have significantly different meanings depending on the other nonverbals with which they're clustered. A "Cluster" is two or more body language configurations seen simultaneously or within a very short time.
In a written & spoken language, a "Homonym" is one of a group words that is spelled the same and pronounced the same - and yet has different meanings. We can call Nora Jones "hot", a red pepper can also be "hot" and it's "hot" outside if the temperature reaches 105 degrees. A parallel phenomenon is seen in Nonverbal communication. A Subtle variation or an identical single body language symbol can have completely different meanings depending on the setting - or the other "words" in the nonverbal sentence.
There are many examples of these Nonverbal Homonyms. One common case in point is lip biting. Biting one's own lip may have sexual & flirtatious implications - but it also may indicate anxiety, fear, intense physical activity or deep thought. Noting the other nonverbals gives context and meaning.
Secret # 411: Lip Biting with Intense Physical Activity
Secret # 531: Sarkozy's Mouth Tells Us What He's Feeling
Secret # 30: Lip Biting on a Defensive Tackle
Secret # 813: Ask Osama Bin Laden Appeasement
Secret # 351: Never Let 'em See You Sweat