Good question. In many contexts they could all mean the same thing, but there can be some small differences. BLAST. When used as a verb, it usually implies the use of explosives such as dynamite. When used as a noun, it can refer to the actual explosion, but often it refers more to the sudden forceful wave of compressed air or energy that spreads out from the explosion. So, for example, you might hear that someone was knocked down by the blast, even though they were not hit by any objects or by the flames. BURST. When used as a verb, it means that something is being broken open suddenly due to a build up of pressure. It would usually not be used when speaking of explosives, but rather too much air pressure or water pressure. For example, a balloon will burst if you blow too much air into it. A dam may burst if there is too much water behind it. When used as a noun, it can refer to the moment of breaking under pressure. But it has another use where it means a sudden and brief occurrence of something. For example, we speak of a burst of laughter, or a burst of noise, or a burst of hard work, or a burst of interest. EXPLODE is always a verb. Its meaning is a bit more general and can include the meanings of both blast and burst. So we can say that a bomb explodes or that a balloon explodes. We can even use it like the second meaning of burst and say things like "the crowd exploded with laughter." The noun form, EXPLOSION, is also quite general. The primary meaning is similar to "blast" and implies something like dynamite, but it has many other uses. It is very common to hear it used for things like "an explosion of joy", "an explosion of laughter", or "an explosion of interest."