In case you didn't know, $host gives data about the scripting host, including the window containing the script's output.  This in turn gives us the width of the window:

$Host.UI.RawUI.WindowSize.Width

From there, we can

function Break-Line {

    # synopsis::

    # [-help]

    #

    # Description::

    # Inserts linefeeds into strings read from STDIN so they wrap nicely

    # for a given PowerShell window's screen geometry

    #

    # Usage::

    # $data | Break-Line

   

    param (

        [switch]$help

    );

 

    if ($help) { return (Get-FunctionHelp -name $MyInvocation.MyCommand.Name); }

 

    $width = $Host.UI.RawUI.WindowSize.Width - 1;

    $input | % {

        $_ = $_ -replace "`t", "    ";

        foreach ($line in $_.split("`n")) {

            $line = $line -replace "\s*$";

            $indent = $line -replace "(^\s*).*", '$1';

            $line = $line -replace "^\s*";

            while ($line.length -gt ($width - $indent.length)) {

                $splitPoint = $width - $indent.length;

                $buffer = $line.SubString(0, $splitPoint);

                $offset = $buffer.lastIndexOf(" ")

                if (($offset -ne -1) -and ($offet -ne ($buffer.length -1))) {

                    $splitPoint = $offset;

                    $buffer = $line.SubString(0, $splitPoint);   

                }

                $line = $line.SubString($splitPoint, ($line.length - $splitPoint)) -replace "^\s*";

                "$indent$buffer";

            }

            "$indent$line";

        }

    }

}