An extremely strong, full and malty dark lager.
Eisbocks are not simply stronger doppelbocks; the name refers to the process of freezing and concentrating the beer. Some doppelbocks are stronger than Eisbocks. Extended lagering is often needed post-freezing to smooth the alcohol and enhance the malt and alcohol balance. Any fruitiness is due to Munich and other specialty malts, not yeast-derived esters developed during fermentation.
Kulmbacher Reichelbräu Eisbock, Eggenberg Urbock Dunkel Eisbock, Niagara Eisbock, Capital Eisphyre, Southampton Eisbock
You can view the complete style details on the BJCP website. The 2008 style guide is obsolete but there is a similar 2015 style that you can view below...