1. [n]  overlapping stitch made by starting next stitch at middle of preceding one
2. [v]  do backstitches

BACKSTITCH is a 10 letter word that starts with B.

1. \Back"stitch`\, n. [Back, adv. + stitch.]
   A stitch made by setting the needle back of the end of the
   last stitch, and bringing it out in front of the end.
   
   

2. \Back"stitch`\, v. i.
   To sew with backstitches; as, to backstitch a seam.