senior partner
noun[C]
ukusamemberof agroupofpeople,companies,countries, etc. that has morepowerandinfluencethan othermembers:
When the US and Japandiscussrulesforfinancialservices, Japan is nowalmosttheseniorpartner.
It wasclearwho theseniorpartnerin thearrangementwas.
one of thepeoplewho hasreachedthetoprankin apartnership:
She is aseniorpartnerin a New Yorklawfirm.
Compare
junior partner