String to put at the start of lines that have been wrapped. Useful values are "> " or "+++ ":

:set showbreak=>\

Note the backslash to escape the trailing space. It's easier like this:

:let &showbreak = '+++ '

Only printable single-cell characters are allowed, excluding <Tab> and comma (in a future version the comma might be used to separate the part that is shown at the end and at the start of a line). The characters are highlighted according to the '@' flag in 'highlight'. Note that tabs after the showbreak will be displayed differently. If you want the 'showbreak' to appear in between line numbers, add the "n" flag to 'cpoptions'. A window-local value overrules a global value. If the global value is set and you want no value in the current window use NONE:

:setlocal showbreak=NONE

(default "")

not available when compiled without the +linebreak feature