What is "sinister base"

Sinister \Sin"is*ter\ (s[i^]n"[i^]s*t[~e]r; 277), a. Note: [Accented on the middle syllable by the older poets, as Shakespeare, Milton, Dryden.] [L. sinister: cf. F. sinistre.]

1. On the left hand, or the side of the left hand; left; -- opposed to dexter, or right. ``Here on his sinister cheek.''
   --Shak.

   My mother's blood Runs on the dexter cheek, and this sinister Bounds in my father's
   --Shak.

   Note: In heraldy the sinister side of an escutcheon is the side which would be on the left of the bearer of the shield, and opposite the right hand of the beholder.

2. Unlucky; inauspicious; disastrous; injurious; evil; -- the left being usually regarded as the unlucky side; as, sinister influences.

   All the several ills that visit earth, Brought forth by night, with a sinister birth.
   --B. Jonson.

3. Wrong, as springing from indirection or obliquity; perverse; dishonest; corrupt; as, sinister aims.

   Nimble and sinister tricks and shifts.
   --Bacon.

   He scorns to undermine another's interest by any sinister or inferior arts.
   --South.

   He read in their looks . . . sinister intentions directed particularly toward himself.
   --Sir W. Scott.

4. Indicative of lurking evil or harm; boding covert danger; as, a sinister countenance.

   Bar sinister. (Her.) See under Bar, n.

   Sinister aspect (Astrol.), an appearance of two planets happening according to the succession of the signs, as Saturn in Aries, and Mars in the same degree of Gemini.

   Sinister base, Sinister chief. See under Escutcheon.