This article is a follow-up on the last one which covered Mula Bandha. There need not be any ambiguity about Uddiyana Bandha at all. There is nothing elusive about it at all.
There are two vastly different types of Uddiyana which are sometimes mixed up. One utilizes suction and the other uses pressure to deform the abdominal cavity. I will here first get the suction-type Uddiyana out of the way and then focus on the pressure-based Uddiyana for the rest of the article.