Noun

1. The distant past beyond anyone's memory.
   • 1904, Arthur Quiller-Couch, Fort Amity, ch. 10:

     Harvests at Boisveyrac had been gathered under arms since time out of mind, with sentries posted far up the shore.

   • 1905, William Butler Yeats, "Red Hanrahan's Curse," in Stories of Red Hanrahan:

     And on the yew that has been green from the times out of mind

     By the Steep Place of the Strangers and the Gap of the Wind.

2. A lengthy duration of time, longer than is readily remembered.
   • 1899, Frank Norris, Blix, ch. 1:

     They were Episcopalians, and for time out of mind had rented a half-pew in the church of their denomination on California Street.

Adverb

1. For a lengthy period of time; on numerous occasions.
   • 1853, Charles Dickens, Bleak House, ch. 1:

     The very solicitors’ boys who have kept the wretched suitors at bay, by protesting time out of mind that Mr Chizzle, Mizzle, or otherwise was particularly engaged and had appointments until dinner, may have got an extra moral twist and shuffle into themselves out of Jarndyce and Jarndyce.

   • 1882, George Bernard Shaw, Cashel Byron's Profession, ch. 13:

     I tell you that Cashel never was beaten, although times out of mind it would have paid him better to lose than to win.