Gradual or plodding but certain to finish, as in Slow but sure this book's getting written. This idiom was first recorded in 1562, although the idea is much older. A related phrase appears in the proverb slow and steady wins the race, which is the moral of Aesop's fable about the race between a tortoise and a hare, which stopped to nap during the race and therefore lost.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.