I agree that the word 'tactical' is often mis and/or over-used, usually to appeal to wannabe warriors like Kyle whatshisname. A search on Amazon.com yields any number and type of equipment that is styled as 'tactical'...
However, the usage of the word used only to apply to equipment that performed a specific offensive/defensive purpose...
: of or relating to combat tactics: such as...
(1) : of or occurring at the battlefront a tactical defense; a tactical first strike,
(2) : using or being weapons or forces employed at the battlefront; tactical missiles
The most extreme usage of the term is seen in "tactical nukes". These were designed for the battle front, but are admittedly a bit of overkill in tank warfare. (Expect to see more usage of this term in the near future.)
[By way of comparison, we also see the term 'Strategic'... Many people do not understand, or cannot explain the difference, and really has no bearing on the topic at hand...]
So what does "tactical" mean more recently?
In the last 20-30 years, the term has been extended to body armor, as well as MOLLE vests and other equipment that attaches to these as used in small arms tactics (such as knives). [See the second image below.]
"The good knife fighter thinks on point and blade and shearing-guard
simultaneously. The point can also cut; the blade can also stab;"
Frank Herbert (Dune)
Knives have many uses, but primarily they are intended for cutting and stabbing. Most people who look at knives with a civilian eye see only the shiny tool that cuts their tomatoes. Professionals such as Chefs think on the cutting edge, and butchers look at the tip, but also the edge.
Some large knives are designed for survival in the field; this may include self-defense.
For example, to the left in the first image below, the heavy ESSE 5S is considered a survival knife. It was designed for RAT SAR, and made to chop its way out of a downed helicopter and also to survive in the field. It's primary purpose is to cut and hack (see: batoning). It includes other features that are non-tactical. It is considered unbreakable, but some old hands may blunt the tip just in case.
The two knives to the right (Gerber StrongArm and Boker Nano L-R) I would consider tactical; notice the spear tip. Its primary purpose is to provide maximum penetration. If you try to chop wood with these they might break. Tactical blades like these are often worn clipped to a Molle vest (see link above, and image below), or even hidden inside a boot.
This is my expert opinion...however, most civilians and even war correspondents may not see the differences, and probably refer to all of these as "tactical".
To make it even more confusing, many manufacturers are combining features , and often describing pretty much anything made for the woods and colored in olive, black or desert tan as 'tactical.
Below is an image of the Gerber clipped to a MOLLE vest.