thumb blue
 靛藍


 Thumb n.  The short, thick first digit of the human hand, differing from the other fingers in having but two phalanges; the pollex. See Pollex.
    Upon his thumb he had of gold a ring.   --Chaucer.
 Thumb band, a twist of anything as thick as the thumb. --Mortimer.
 Thumb blue, indigo in the form of small balls or lumps, used by washerwomen to blue linen, and the like.
 Thumb latch, a door latch having a lever formed to be pressed by the thumb.
 Thumb mark. (a) The mark left by the impression of a thumb, as on the leaves of a book. --Longfellow. (b) The dark spot over each foot in finely bred black and tan terriers.
 Thumb nut, a nut for a screw, having wings to grasp between the thumb and fingers in turning it; also, a nut with a knurled rim for the same perpose.
 Thumb ring, a ring worn on the thumb. --Shak.
 Thumb stall. (a) A kind of thimble or ferrule of iron, or leather, for protecting the thumb in making sails, and in other work. (b) Mil. A buckskin cushion worn on the thumb, and used to close the vent of a cannon while it is sponged, or loaded.
 Under one's thumb, completely under one's power or influence; in a condition of subservience. [Colloq.]