When conversing, what is a "big resistor"?
It can mean either, depending on the conversation, or it can mean able to dissipate a lot of heat (high power rating). Within "normal" circuit design these days, it probably means a high resistance, but in these days of semi-microscopic surface-mount parts (an 0201 part is only 0.6 mm long and 0.3 mm wide) using something like a 2512 may well cause a comment, like "Do you really need that big a resistor?).

If you're into heavy metal power engineering, well, they talk a language of their own. Here, for instance is a Dynamic Braking Resistor for electric locomotive use, which is 5 1/2 inches high, 14 inches wide, and 12 1/4 inches deep, with a peak power rating of 84 kW, and it probably counts as a "big resistor", even though its resistance is less than 1 ohm. It also requires (although it's not stated) plenty of room around it for airflow.

ETA - If the "bigness" of the resistor comes up in conversation, this probably means that whichever attribute is being discussed is cause for concern, and that depends entirely on the circuit or system involved.

For instance, the 85 kW resistor mentioned is going to need a lot of cooling, and a lot of space. If the system involved is not a locomotive, but instead it's an electric car which uses the resistor for braking (the development team just happens to have one of these monsters on hand), somebody might well object that it's too big.

On the other hand, if an op amp is being used which has bias or offset currents of 100 nA, and a feedback resistance of 10 Mohm, somebody is likely to object that the resistor is too big, since it will produce offsets in the volt range.

It all depends on context.