The phrase "a second update" is correct and usable in written English.
You can use it when referring to the second occurrence of an update or revision on a particular topic or project.
Example: "We are pleased to announce a second update on the progress of our software development."
Alternatives: "a follow-up update" or "an additional update."
Yesterday, Apple made a rare apology over the iOS 8.0.1 software glitch, launching a second update to restore full functionality to the tens of thousands of affected phones, while playing down concerns about the "bendy" iPhone 6 Plus.
Apple has released a second update to its new iOS 8 iPhone software in two days after its iOS 8.0.1 update that left iPhone owners unable to make calls or use their Touch ID fingerprint sensors, which was withdrawn.
Peek also added a second update in the form of more robust image support.
A second update later in the year will also enable downloadable watch faces.
Update 2: A second update on the fabulis blog says a representative has called and apologized.
A second update was posted the following day, expanding on the denial but still tucked away at the bottom, and still refusing to accept that the story was total, unsupported bullshit.
Broadcom's chips also use a preliminary version of a faster, 54-megabit-a-second update called 802.11g.
(A second, updated edition will come out this year).
A second, updated edition, in which he was joined by Dr. Tobin as editor, appeared in 1997 in two volumes.
Tom Dame, who also came to Harvard from Columbia at that time, has coordinated telescope observations over the last decade, resulting in a second, updated map of the Milky Way, published in 2001.
2015 marked the arrival of the third edition of this masterpiece (a second updated and expanded edition appeared in 2002).
