Verb fossilise has 2 senses

• fossilise(v = verb.change) fossilize - convert to a fossil; "The little animals fossilized and are now embedded in the limestone"
is one way to convert
Derived form noun fossilisation₁
Sample sentences:
Something ----s
Something ----s something

• fossilise(v = verb.change) fossilize - become mentally inflexible; Array
is one way to age, get on, maturate, mature, senesce
Derived form noun fossilisation₂
Sample sentence:
Somebody ----s