URACIL By N., Pam M.S. - April 29, 2013 noun. a pyrimidine substance which is one out of the four bases housed in RNA. With regard to DNA, thymine takes place rather than uracil. URACIL: "Tomorrow, we will be testing the effectiveness of uracil on the cells." Related Psychology Terms THYMINE CYTOPLASMIC VASOPRESSIN TRANSCRIPTION TRANSLATION VAGINA DENTATA SUBSTANCE ABUSE ADJUNCT UNCUS RADIOIMMUNOASSAY (RIA) Cite this page: N., Pam M.S., "URACIL," in PsychologyDictionary.org, April 29, 2013, https://psychologydictionary.org/uracil/ (accessed October 19, 2019).