Definition of "selector"

There is one selection for hot chocolate. All selectors are the push button type.

1949, Billboard, volume 61, number 34, page 97

The ID selector targets just one element per page, making it much more specific than a class selector that might target many.

2007, Craig Cook, David Schultz, Beginning HTML with CSS and XHTML, Apress, page 28

The selector indicates the query expression to run over the DOM; the context indicates the portion of the DOM from which to run the query.

2009, Dino Esposito, Microsoft ASP.NET and AJAX, Microsoft Press, page 140

Phar Lap executables […] provide a protected-mode selector, 34h, that maps to the first megabyte of physical memory.

1990, Byte, volume 15, numbers 11-13, page 256

You will only have to be concerned with DPMI, selectors, and such, if you use Borland C++ in DOS.

1995, Lary L. Myers, Keith Weiskamp, Amazing 3-D games adventure set, page 235

Gopher selector strings are more liberal in makeup than URLs and may contain any characters other than a tab, return, or linefeed.

1996, Kenneth H. Rosen, UNIX System V, Release 4: An Introduction, McGraw-Hill Osborne Media, page 438

That's my sector, homosexual dissector / Come again, rewind selector

2009, “Medicine Ball”, in Relapse, performed by Eminem

This sonic body has to decide which music track to play at any particular moment. But when the selector is alone in front of the crowd, how do they know which track to play next?

2011, Julian Henriques, Sonic Bodies, A&C Black, page 125

Each selector in turn chose the particular allotment he wanted for his client, and so on till this important work was over.

1887, Harriet W. Daly, Digging, Squatting, and Pioneering Life in the Northern Territory of South Australia, page 78