imperturbable (adj.)

• balanced
• bovine
• collected
• complacent
• composed
• cool
• dispassionate
• dull
• even-tempered
• fast
• fiducial
• firm
• impassive
• nonchalant
• patient
• predictable
• reliable
• secure
• self-satisfied
• smug
• solid
• sound
• stable
• steadfast
• steady
• stoic
• stolid
• substantial
• unaffected
• unflappable
• unflinching
• unmoved
• unshakable
• untouched
• unwavering
• well-balanced