equable

adj. uniform, regular, even, steady

(a.)
Uniform in action or intensity; not variable or changing; -- said of the feelings or temper.
  

(a.)
Equal and uniform; continuing the same at different times; -- said of motion, and the like; uniform in surface; smooth; as, an equable plain or globe.
  

Adjective
1. not varying; "an equable climate"
(similar) temperate
2. not easily irritated; "an equable temper"; "not everyone shared his placid temperament"; "remained placid despite the repeated delays"
(synonym) even-tempered, good-tempered, placid
(similar) good-natured