'are generally defined' is correct and usable in written English.
You can use it when referring to a group or concept that is generally understood to have a certain definition or meaning. For example: National parks are generally defined as areas of land protected by the government for public use and enjoyment.
Psychometric properties are generally defined based on highly controlled assessments and results cannot be generalized to clinical practice.
(Baby boomers are generally defined as people born in 1946 through 1964).
Sports drinks are generally defined as sweetened drinks with electrolytes; enhanced waters have vitamins instead.
Microprocessors are generally defined by the number of pieces of information they can manipulate at once.
Since then, however, 11 additional states, including New York, have adopted laws prohibiting execution of the retarded, who are generally defined as people with I.Q.'s below 70.
Trees are generally defined as woody plants more than 6 m tall, having a dominant stem, or trunk, and a definite crown shape.
Football Outsiders found that this proved true in the N.F.L.: "championship teams are generally defined by their ability to easily win games over inferior teams".
Several Asian markets are approaching bear markets, which are generally defined as a 20 percent drop in share prices from their near-term peak.
Green buildings are generally defined as those that use energy more efficiently than those with conventional designs and that provide workers with well-lighted spaces furnished with an abundance of clean air.
Natural foods are generally defined as minimally processed without artificial additives, while organic foods are certified by the Agriculture Department as produced in an environmentally sustainable way without chemicals, hormones, antibiotics, genetically modified organisms or radiation.
Under the law, dietary supplements are generally defined as products that contain or are derived from natural foodstuffs like minerals or herbs and do not claim to prevent, mitigate or cure specific illnesses.
