The definition for incumbent is "Necessary as a duty or responsibility." Used in a sentence: It was incumbent on Jack to attend his father's retirement party.

The definition for insinuate is "To suggest indirectly." Used in a sentence: Sinead, who did not like confrontation, insinuated that Beth was lying.

The definition for placebo is "An inactive substance used in medical testing." Used in a sentence: Tom, who had taken the placebo, found that his allergy symptoms did not go away.

The definition for stifle is "To repress or discourage." Used in a sentence: Amy tried ineffectively to stifle her giggles after she read Susan's note in class.

The definition for untenable is "Not able to be defended." Used in a sentence: Rashid made the untenable statement that George Washington was the second president of the United States.