|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|a chattering or flighty, light-headed person.|
|1.||threatening or suggesting evil or harm; ominous: a sinister glance|
|2.||evil or treacherous, esp in a mysterious way|
|3.||(usually postpositive) heraldry of, on, or starting from the left side from the bearer's point of view and therefore on the spectator's right|
|4.||archaic located on the left side|
|5.||archaic (of signs, omens, etc) unfavourable|
|[C15: from Latin sinister on the left-hand side, considered by Roman augurs to be the unlucky one]|
sinister sin·is·ter (sĭn'ĭ-stər)
Presaging trouble; ominous.
On the left side; left.