There are several antonyms for the word "up casts," which refers to throwing something upwards or raising it to a higher level. The opposite of up casting would be down casting, which involves throwing something downwards or lowering it to a lower level. Other antonyms include lowering, decreasing, reducing, dropping, descending, and falling. These terms represent the opposite actions to up casting, which could be used in a variety of contexts. For example, reducing or lowering prices instead of raising them could be antonyms to up casting prices. Similarly, rather than throwing an object up, one could drop or lower it down.