noun The shortest and thickest digit of the hand that for humans has the most mobility and can be made to oppose (moved to touch) all of the other fingers.
noun The part of a slider that may be moved linearly along the slider.
a scroll-bar thumb
noun A thumbnail picture.
noun A top hatch plate for covering an excavator bucket, used to keep material in the digger bucket after scooping it up, and not letting it spill out.
verb To touch or cover with the thumb.
to thumb the touch-hole of a cannon
verb To turn the pages of (a book) in order to read it cursorily.
thumb through
verb To gesture with the thumb, for example when flagging a ride.
verb To hitchhike.
So I started thumbin' back east, toward my hometown.