What is the interpretation of a wife's trembling when any part of her body is touched?

A woman is not required to perform ghusl (definition) unless she is certain of the emission of semen, in accordance with the Prophet's saying, "Water [ghusl] is from water [semen]," or due to sexual intercourse, even if ejaculation does not occur. However, if a fluid other than semen is discharged: if it is madhy (pre-seminal fluid) or wady (thick white fluid often discharged after urination), it is impure and nullifies wudu, and the body and clothing must be purified from it. If it is vaginal discharge, it is pure according to the preponderant opinion, but it does nullify wudu. If nothing is discharged, then nothing is required of her.