Traditionally, the executive and (one hopes!) senior technical review of the completed proposal. Generally shortened to Red Team.
In this usage, Red Team is the final review that can amend content before the proposal is submitted to the client. Subsequent reviews and changes should be limited to presentation niceties.
Postscript: This definition, and the associated one for Red Team, are from my book “Proposals: Getting Started, Getting Better.” I still concur with that 2014 view of my world, but see it as a wee bit messier than I did then.