I define startup speed as…
-- The rate of strategic value delivery to users --
Let's unpack it...
"The rate" - the consistency and interval of events
"Strategic value" - units of value that are aligned with your vision and long-term self-interest (not just doing anything for anyone)
"To users" - not for academics, partners, regulators, internal people, or otherwise
It is NOT busywork, focusing on more than one thing at a time, and/or living in chaos and thrash.