to and fro

to-and-fro (all parts of speech except adverb)

to and fro (not comparable)

1. (dated) back and forth; with an alternating motion.
   • 1883, Robert Louis Stevenson, chapter 4, in Treasure Island:

     A light tossing to and fro and still rapidly advancing showed that one of the newcomers carried a lantern.

   • 1885, Richard F. Burton, The Book of the Thousand Nights and a Night:

     But presently the fumes of the wine rising to his head, he became helplessly drunk and his side-muscles and limbs relaxed and he swayed to and fro on my back. When I saw that he had lost his senses for drunkenness, I put my head to his legs and, loosing them from my neck, stooped down well-nigh to the ground and threw him at full length, […]

   • 1886, John Burroughs, Winter Sunshine, page 13:

     He bends his knees more than the white man, and oscillates more to and fro, or from side to side.

   • 1979, National Academy of Sciences (U.S.), IEEE Electrical Insulation Society, tAnnual report - Conference on Electrical Insulation and Dielectric Phenomena, page 396:

     Even charges hopping on a larger array of localized sites than the two sites in (ii) execute normally many more to-and-fro oscillating motions than ...

to and fro (third-person singular simple present tos and fros or to and fros, present participle toing and froing or to and froing, simple past and past participle toed and froed or to and froed)

1. To go back and forth; to alternate.
   • 2015, Barbara Taylor, The Last Asylum: A Memoir of Madness in Our Times

     "For a while I didn't tell anyone on the ward where I was going, but my toing and froing made people curious and eventually I confided in a few."

to and fro (not comparable)

1. (dated) Pertaining to something or someone moving forward and back to the same position.
   • 1847, Peter Mere Latham, Lectures on subjects connected with clinical medicine, comprising diseases, page 90:

     The next day he had more power of moving his limbs, and the to and fro sound was thought to be a little less distinct.

to and fro (plural to and fros or tos and fros)

1. (dated) The movement (of someone or something) forward followed by a return to the same position. May refer to a concept such as an emotional state or a relationship as well as a physical thing.
   • 1849, Ralph Erskine, Gospel sonnets; or, Spiritual songs, page 233:

     My life's a maze of seeming traps, A scene of mercies and mishaps; A heap of jarring to and fros, A field of joys, A field of woes.