Linethrough/strikethrough a whole HTML table row

Oh yes, yes it is!

CSS:

table {
    border-collapse: collapse;
}

td {
    position: relative;
    padding: 5px 10px;
}

tr.strikeout td:before {
    content: " ";
    position: absolute;
    top: 50%;
    left: 0;
    border-bottom: 1px solid #111;
    width: 100%;
}

HTML:

<table>
    <tr>
        <td>Stuff</td>
        <td>Stuff</td>
        <td>Stuff</td>
    </tr>
    <tr class="strikeout">
        <td>Stuff</td>
        <td>Stuff</td>
        <td>Stuff</td>
    </tr>
    <tr>
        <td>Stuff</td>
        <td>Stuff</td>
        <td>Stuff</td>
    </tr>
</table>

http://codepen.io/nericksx/pen/CKjbe

My answer (below) said that it is not possible. I was wrong, as pointed out by @NicoleMorganErickson. Please see her answer (and upvote it!) for how to do it. In short, you use :before pseudo-class to create an element that draws a border across the middle of the cell, above the content:

table           { border-collapse:collapse } /* Ensure no space between cells   */
tr.strikeout td { position:relative        } /* Setup a new coordinate system   */
tr.strikeout td:before {                     /* Create a new element that       */
  content: " ";                              /* …has no text content            */
  position: absolute;                        /* …is absolutely positioned       */
  left: 0; top: 50%; width: 100%;            /* …with the top across the middle */
  border-bottom: 1px solid #000;             /* …and with a border on the top   */
}    

(original answer)

No, it is not possible using only CSS and your semantic table markup. As @JMCCreative suggests, it is possible visually using any number of ways to position a line over your row.

I would instead suggest using a combination of color, background-color, font-style:italic and/or text-decoration:line-through to make the entire row obviously different. (I'd personally strongly 'fade out' the text to a color much closer to the background than normal text and make it italic.)

tr {
    background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQIW2NkYGCQBAAAIwAbDJgTxgAAAABJRU5ErkJggg==');
    background-repeat: repeat-x;
    background-position: 50% 50%;
}

I used http://www.patternify.com/ to generate the 1x1 image url.