'Sinister base' definitions:

Definition of 'Sinister base'

From: GCIDE

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. [1913 Webster]
My mother's blood Runs on the dexter cheek, and this sinister Bounds in my father's --Shak. [1913 Webster]
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. [1913 Webster]
2. Unlucky; inauspicious; disastrous; injurious; evil; -- the left being usually regarded as the unlucky side; as, sinister influences. [1913 Webster]
All the several ills that visit earth, Brought forth by night, with a sinister birth. --B. Jonson. [1913 Webster]
3. Wrong, as springing from indirection or obliquity; perverse; dishonest; corrupt; as, sinister aims. [1913 Webster]
Nimble and sinister tricks and shifts. --Bacon. [1913 Webster]
He scorns to undermine another's interest by any sinister or inferior arts. --South. [1913 Webster]
He read in their looks . . . sinister intentions directed particularly toward himself. --Sir W. Scott. [1913 Webster]
4. Indicative of lurking evil or harm; boding covert danger; as, a sinister countenance. [1913 Webster]
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. [1913 Webster]