space bar

WordReference Random House Unabridged Dictionary of American English © 2025

space′ bar′, 

1. Computing a horizontal bar on a typewriter keyboard that is depressed in order to resume typing one space to the right.
2. Computing a horizontal bar on a computer keyboard that is depressed in order to move the cursor one space to the right or, often, to perform some function in a program.
• 1885–90

Collins Concise English Dictionary © HarperCollins Publishers::

space-bar noun

1. a horizontal bar on a typewriter or computer keyboard that is depressed in order to leave a space between words, letters, etc