sǐ​bǎn

inflexible

死板 sǐ​bǎn
inflexible adjective
stubbornly adhering to rules or methods; unwilling to adapt to circumstances

He is too rigid in his ways and doesn't know how to adapt.

stiff adjective
lacking in variety, vitality, or expressiveness; mechanical in style

This painting is too stiff; it isn't vivid at all.

Frequency

Movie subtitles
1.76 per million appears in 1% of films
Written text
1.07 per million

Sources

Definitions
CC-CEDICT