The word "abasic" is relatively uncommon and has few synonyms. It is usually used in relation to biology or chemistry, referring to a molecule that is missing a nitrogenous base. A similar term is "aplastic," which also refers to a deficient or absent portion of a molecule. Other possible synonyms for "abasic" could include "incomplete," "deficient," or "lacking," depending on the context in which the word is being used. However, because "abasic" is a technical term with a specific meaning, it may be more appropriate to use it in scientific writing and communication rather than trying to find an equivalent synonym.