adjective / verb / adverb
firm
FURM/fˈɝm/
Stable enough to resist pressure or change.
The wooden post remains firm as an adult pushes against it.

Etymology
Latin firmus covered both physical stability and figurative steadfastness. That breadth survives in English: a firm object resists movement, while a firm decision resists change.
In context
Be steady to your purposes and firm as a rock this ice is not made of such stuff as your hearts may be it is mutable and cannot withstand you
More examples
- She firms the soil around each seedling with her hands.
- Our departure date is firm, even if the weather changes.
- They stand firm despite pressure to accept a lower price.
Forms
firm · firmer · firmest · firms · firmed · firming
firmness noun — The quality of resisting pressure or change.
firmly adverb — In a steady or unyielding way.