They tend to be contrived, artificial, aggressively timeboxed, unrealistically isolated from normal tools one might use, and the desired solution tends to be one that depends on having one or two central creative insights.

Whether they’re a good or bad interviewing technique is a separate topic — I only mean to describe the usage of the term as I’ve seen it in the last 5-10 years.

(Also, to be clear, not every question asked by Google necessarily falls into this category. System design questions in particular tend not to.)