Adverb modifying a verb:
* I am terribly sorry for the mistake.
* The movie was terribly boring.
* She sang terribly out of tune.
Adverb modifying an adjective:
* The weather was terribly cold.
* He was terribly frightened by the loud noise.
* The news was terribly sad.
Adverb modifying another adverb:
* I was terribly slowly making my way through the crowd.
* The children were terribly quietly playing in the corner.
Note: "Terribly" can also be used to express strong feeling or emotion, even if the action itself isn't inherently bad. For example:
* "I'm terribly excited to go on vacation!"
* "We were terribly happy to see you."