International Data Corp. (IDC) reports that 10.1 million “media tablets” shipped in the fourth calendar quarter of 2011. Apple’s share of that pie dropped from 93 percent in the previous quarter to 73 percent, according to the report, but IDC says that Apple still has a “strong leadership position” in the media tablet market that it will retain throughout 2011.

[ad#Google Adsense 300×250 in story]IDC says that Samsung’s Galaxy Tab device was Apple’s primary competitor for the holiday season, and captured more than 17 percent marketshare. “A number of smaller regional players also participated.”

IDC explained its definition of “media tablets” thus: “media tablets are tablet form factor devices with color displays larger than 5 in. and smaller than 14 in. running lightweight operating systems (such as Apple’s iOS and Google’s Android OS) and can be based on either x86 or ARM processors.”

IDC differentiates “media tablets” from “tablet PCs,” which it says “run full PC operating systems and are based on x86 processors.” Media tablets are also different from eReader devices like Amazon’s Kindle or the Barnes & Noble Nook, which are “single purpose–focused devices.”

Looking forward, IDC expects Apple to retain 70 – 80 percent marketshare in 2011 with the release of the iPad 2, thanks to its release into the market at a time “before most competitors come to market with first generation media tablets.”

Competition for Apple to look out for, IDC opines, includes Samsung’s forthcoming 10.1-inch Galaxy Tab running Android 3.0 “Honeycomb,” the same operating system powering Motorola’s Xoom, which IDC also counts as competition. Regarding the Xoom, IDC says its “relatively high price is expected to be a barrier to gaining significant share.”

IDC expects the second half of 2011 to heat up with other vendors and designs. “One differentiation path that some vendors are likely to take is to focus on specific market segments, such as commercial. While benefitting from unique product positioning, they are likely to address a smaller overall market and will need to be competitive with devices from Apple and others,” reads the report.