big enough and ugly enough vs senior

big enough and ugly enough

• Mature, grown-up, old enough (with the implication that one can look after oneself and make one's own decisions). 

senior

• Older; superior 

• Higher in rank, dignity, or office. 

• Of or pertaining to a student's final academic year at a high school (twelfth grade) or university. 

• Somebody who is higher in rank, dignity, or office. 

• A final-year student at a high school or university. 

• Someone seen as deserving respect or reverence because of their age. 

• An old person. 

• Someone older than someone else (with possessive).