thumb·print 
/ˈθʌmˌprɪnt/ noun
plural thumb·prints /ˈθʌmˌprɪnt/ noun [count] : the pattern of marks made by pressing your thumb on a surface : a fingerprint made by a thumb
▪ He left a dirty thumbprint on the page. — sometimes used figuratively ▪ Her thumbprints are all over this project. [=it is obvious that she was very involved in this project]
▪ He left a dirty thumbprint on the page. — sometimes used figuratively ▪ Her thumbprints are all over this project. [=it is obvious that she was very involved in this project]
