catastrophic
The definition for catastrophic is "Relating to extreme misfortune." Used in a sentence: The effects of the massive hurricane were catastrophic.
colossal
The definition for colossal is "Immense, enormous." Used in a sentence: After pushing with all his might, Frank realized he could never move the colossal boulder.
demeanor
The definition for demeanor is "Behavior towards others." Used in a sentence: Carlos was well liked because of his charming demeanor.
diffident
The definition for diffident is "Lacking self–confidence." Used in a sentence: The diffident student never raised her hand in class, even when she knew the answer.
heed
The definition for heed is "To pay attention to." Used in a sentence: "Heed my advice," the fortuneteller warned Sebastian when he tried to ignore her prophecy.