unsplit

un- +‎ split

unsplit (not comparable)

1. Not split; whole, undivided.

unsplit (third-person singular simple present unsplits, present participle unsplitting, simple past and past participle unsplit)

1. (transitive) To undo the splitting of.
   • 1963, New Mexico Transporter:

     Like it or not, we are in a motor age and we can no more turn back the clock than we can unsplit the atom.

   • 2012, Lee Lanier, Digital Compositing with Nuke:

     To unsplit the split, click on the View Menu buttons and choose Unsplit Left/Right (v6.2) or Unsplit Main (v6.3).

• puntils, unspilt