1.
If you ~ something or if it firms up, it becomes firmer and more solid.
This treatment helps tone the body, ~ muscles and tighten the skin...
I now go swimming five times a week, which helps firm me up...
The mixture will seem too wet at this stage, but it will ~ when chilled.
PHRASAL VERB: V P n (not pron), V n P, V P
2.
If you firm something up or if it firms up, it becomes clearer, stronger, or more definite.
Looking to the future, the Government will ~ their plans for a cleaner, greener, safer Britain...
At least the bank situation had firmed up.
PHRASAL VERB: V P n (not pron), V P, also V n P
3.
If a financial institution firms up the price or value of something, they take action to protect and maintain its price or value.
OPEC has agreed to freeze its global oil production slightly in order to ~ crude prices.
PHRASAL VERB: V P n (not pron)