se ‧ nes ‧ cent /səˈnes ə nt, sɪˈnes ə nt/ BrE AmE adjective technical
[ Date: 1600-1700 ; Language: Latin ; Origin: present participle of senescere 'to grow old' , from senex ; ⇨ ↑ senior 1 ]
becoming old and showing the effects of getting older SYN ageing :
a senescent industry
—senescence noun [uncountable]