Multiple definitions of frailty are used. We sought to quantify the frequency that frailty is insufficiently defined in published abstracts. We conducted a systematic review of MEDLINE/PubMed for English abstracts of original research investigating frailty as an exposure or outcome in humans from 2015–2017. A complete definition of frailty included: 1) a named measure of frailty, including “frailty” alone, 2) details on variables included (e.g. grip strength), 3) number of variables included (e.g. 33-item frailty index), and 4) details on cutoffs or levels of frailty unless a definition was used continuously. Our search yielded 1,110 titles; 490 abstracts met review criteria, 348 abstracts had any definition of frailty and were included. Majority reported a single measure of frailty (n=313, 90%). The most commonly used measures were variations of Fried’s phenotype (n=167, 48%) and Rockwood’s cumulative deficit model (n=101, 29%). Only 56 abstracts had complete definitions (16%). In 123 abstracts (35%), a means of measuring frailty was named, but no additional details were given. When details of the frailty measure were described, they generally referred to cutoffs or levels rather than variables used in the measure. A minority of abstracts of original manuscripts related to frailty research had adequate definitions of frailty. We encourage scientists to adopt a standardized approach to defining the term for all abstracts related to frailty research to facilitate systematic reviews, meta-analysis, and accurate reporting of frailty science.