What is the defining characteristic of tibbles in R?

The defining characteristic of tibbles in R is that they are streamlined data frames. Tibbles are an enhancement over traditional data frames, designed to make data handling more efficient and user-friendly. They provide clear printing methods that show only a subset of rows and columns, as well as better handling of column types, which helps avoid common pitfalls when working with large datasets.

Tibbles also allow for the use of non-standard column names and make subsetting data easier without altering the original data structure. This streamlined functionality promotes better practices in data analysis, making the process more intuitive for users.