I often come across this term "Strobist" in Macro Photography and other equipment related to it. What does Strobist actually mean?
"Strobists" are the followers of teachings of David Hobby published in his blog, "The Strobist". Strobism is usually characterized by using small flashes (designed for on-camera use) in manual mode off camera to achieve better lighting than available from ambient lighting. The flashes are often accompanied by portable and/or DIY light modifiers and set-up gear.
In recent years, studio strobes (still in manual mode) have also been discussed in Strobist articles. The earlier articles (in "Lighting 101" and "Lighting 102" series) are still relevant and give a sound base for anyone wanting to get in command over their lighting, even if manual mode is not the ultimate goal.
You might run into the term in macro photography because more light is often welcome for macro, so cheap and flexible ways of creating and controlling it are nice to know. Originally strobism, however, is mostly concentrated on on-site (off-studio) portraiture. The techniques require some time to set up and adjust equipment with a specific outcome in mind, so they are more suitable for arranged shots than live event coverage.
A strobist is someone who uses off-camera flash (flashguns/speedlights rather than studio strobes) for lighting. Compared to studio strobes, it's the relatively low-cost and relatively portable option.
"Strobist" refers to a blog maintained by photojournalist turned educator David Hobby.
The original by-line on the blog sums up strobist philosophy quite nicely:less gear, more brain, better light.
Originally it was about eschewing big AC studio strobes (and studios in general) leveraging the growing powers of digital photography to do more with smaller lights, making the environment and ambient light do more work for you and increasing mobility and creativity as a result.
Since then the blog has covered how to use studio strobes and has become more about lighting in general, and the by-line has changed to learn how to light.
A strong DIY ethos is also present in the "strobist" movement when it comes to lighting modifiers and other pieces of traditionally very expensive equipment. Due to the popularity of the blog several manufacturers have since jumped in to fill the void with affordable offerings.