The Federal Circuit recently held that a patentee acted as its own lexicographer to define a claim term even though it did not explicitly define the term. Rather, because the patentee consistently and clearly used two terms interchangeably to describe the same structural feature and did so in all of the embodiments in which the feature appeared, the patentee impliedly gave the term its own, unique definition.
In this appeal from a district court litigation, the parties disputed the construction of the term “outer frame” in a patent directed to a transcatheter aortic valve replacement device. At the district court, the patentee argued that “outer frame” should be given its plain and ordinary meaning, while the defendant sought a narrower construction limiting the “outer frame” to a “self-expanding frame having a generally hourglass shape that is positioned outside the inner frame.” In construing the term, the district court found the patentee acted as its own lexicographer and redefined the term “outer frame” to mean a “self-expanding frame.” The district court based its construction on the patentee’s use of the terms “outer frame,” “self-expanding frame” and “self-expanding outer frame” interchangeably when describing two embodiments in the specification.
On appeal, the Federal Circuit affirmed the district court’s construction. The court explained that, while claim terms generally carry their ordinary meaning, a patentee may act as its own lexicographer if the patent’s written description clearly sets forth a definition that departs from that ordinary meaning. The redefinition, however, need not be explicit. A patentee can implicitly redefine a term if the implied definition is so clear that a skilled artisan would understand that it equates to an explicit one. But just referring to two terms as alternatives is not enough. The patent must clearly and consistently use the terms interchangeably in a manner that equates the terms as the same.
Here, the Federal Circuit agreed with the district court and held that because the specification repeatedly uses the terms “outer frame,” “self-expanding frame” and “self-expanding outer frame” interchangeably when describing similar structures in different embodiments, the patentee impliedly gave those terms the same meaning. The court reasoned that this consistent usage, coupled with other undisputed language requiring the outer frame to expand, would lead a skilled artisan to understand that the outer frame was necessarily self-expanding. This result was further supported by the fact that the patent consistently conveys that the self-expanding nature of the outer frame is present in all embodiments.
Practice Tip: A patentee’s redefinition of a claim term need not be explicit. Consistent and clear interchangeable use of terms in the specification can amount to an implied redefinition. Thus, it is important to review language in a specification to identify where terms are used interchangeably as opposed to alternatively. One way to evaluated whether terms are used interchangeably is to identify whether a particular characteristic is present in every embodiment—if so, this may indicate that the feature, such as an outer frame, is defined by that characteristic, such as the ability to be self-expanding.
Aortic Innovations LLC v. Edwards Lifesciences Corp., No. 2024-1145, 2025 WL 2999367 (Fed. Cir. Oct. 27, 2025)