Gifted is typically the top 2%, approximately IQ 130-132 and up. This page of Hoagies Gifted Education Page summarizes it well: What is Highly/Exceptionally/Profoundly Gifted? What Does It Mean?

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they use the term "profoundly gifted" despite having no evidence... They're the reason teachers think we all believe our kids are gifted.
While I would tend to agree, some may say that their "evidence" is a match in behavior characteristics to common lists of gifted traits, rather than evidence of IQ test scores as a measure of being intellectually gifted.

Others believe that high achievement, as a result of participation in a large number of opportunities afforded through high SES, or hot-housing by Tiger Moms, are evidence of giftedness. They may associate "prominence" with gifted.

Possibly in response to those who ascribe to hot-housing, including extensive IQ test prep, there has been an attempt to refine that gifted kids don't just learn more information (and repeat it back like parrots, following rote memorization) but rather they process information differently, creatively, making many connections which others may not have considered. Many have come to understand that gifted is a way of thinking. This reinforces that hot-housing doesn't make a kid become "gifted". However, over time some have deconstructed and analyzed the creative thinking process, and children can now be taught/coached in this as well.

Some kiddos, when tested, are found to be globally gifted (gifted in each area assessed by IQ tests), others are found to have slow processing speed and low working memory and may have a General Ability Index (GAI) calculated if the Full Scale IQ (FSIQ) is found to be invalid. Conversely, some "obviously gifted" kiddos may have exceptionally high processing speed and large working memory, but other scores may be average.

Then there are fabulously talented kids, like Jackie Evancho, who would easily be described as a "gifted" singer, regardless of IQ tests.

Here is an archived definition of gifted as asynchronous, developed by The Columbus Group.

This archived article includes a chart comparing high achievers, gifted learners, and creative thinkers