De falcate is a word that is not commonly used in everyday language. It refers to an object or body part being shaped like a sickle or curved blade. The antonyms of de falcate would be words that describe shapes that are opposite to being curved or sickle-shaped. These could include straight, even, flat, or linear. For example, a straight line would be the opposite of a de falcate shape. It is important to note that not all words have direct antonyms, and in some cases, the opposite concept may not be encapsulated in a single word.