"OhThatsBig" is a term used in the adult entertainment industry to describe a particular category or theme in pornography. It specifically refers to scenes where performers with larger than average body parts (usually penises) are involved, often in conjunction with smaller partners for enhanced visual impact and the sense of dominance. This tag generally indicates that the video will feature size differences and may emphasize the "wow" or "ooh" factor in response to the size of the performers' body parts. It is meant for adult audiences who appreciate this particular aspect of sexual content.