Irascibleness is defined as having a tendency to easily become angry or irritable. Therefore, some possible antonyms for this term might include patience, calmness, tranquility, composure, and even-temperedness. These words describe a state of mind that is much more peaceful and serene than irascibility, and are often associated with individuals who are able to maintain their cool even in stressful situations. Other potentially relevant antonyms might include magnanimity, generosity, and forgiveness - these terms imply a willingness to overlook small annoyances or offenses and move past them without undue resentment or anger. Ultimately, the opposite of irascibleness is a personality that is characterized by its ability to remain calm, composed, and forgiving even in the face of adversity.