gccTLD or Generic Country Code Top Level Domain refers to certain country code TLDs (ccTLDs) which Google considers to be more like traditional generic TLDs (gTLDs) rather than "country" targeted ones, and treats them accordingly for purposes of search engine optimization and indexing.
Some ccTLDs that are considered to be gccTLDs by Google include: (.ad), (.as), (.bz), (.cc), (.cd), (.co), (.dj), (.fm), (.io), (.la), (.me), (.ms), (.nu), (.sc), (.sr), (.su), (.tv), (.tk), (.ws). This list can be found on Google's website.
References
GccTLD Wikipedia(Text) CC BY-SA