Room temperature refers to the temperature of what is considered to be a 'normal'
room. The possibility that your room may be just above freezing or a
sauna is irrelevant.
Physicists usually consider room temperature to be between 21°C and
23°C (294 to 296 Kelvin or 70°F to 74°F), with the implicit
assumption that the room's air pressure is close to standard pressure. In
practice, many physics experiments are not particularly temperature sensitive
— in a laboratory report, "at room temperature" usually means "no
effort was made to control the temperature because it is not considered to be a
significant source of experimental error".
The standard room used by chemists can be slightly warmer. Many European
chemical data sheets list properties of materials at 25°C (298K or
77°F) and one atmosphere. Again, though, "at room temperature" implies a
lack of specific temperature controls beyond, perhaps, basic air conditioning
or a radiator on a thermostat.
When it comes to wine, things get considerably trickier. It is well known
that most red wine should be served at room temperature. However, the room
in question here is not your kitchen or dining room; rather, it refers to
the temperature of your wine cellar. The archetypical wine cellar is underneath
the house, has stone walls and is not directly heated to the same degree as
rooms that are for living.
To complicate things further, different grapes and styles of wine are best
stored and served at different temperatures. For Bordeaux reds and higher
quality new world wines made from merlot or shiraz / syrah, 'room
temperature' is around 18°C. For Burgundy reds and lighter new world
wines, it is between 15°C and 17°C. For Anjou and Beaujolais reds,
room temperature can be as low as 12°C.
For food, room temperature is the temperature reached by food when it has been left to stand for a length of time, often after either cooling or heating. A good metric is chocolate-based desserts. If they melt, your room is probably too warm; if they are hard and crunchy, your room may be too cold.
For those making toys, furniture or other household goods, room
temperature must cover a far broader range. Realistically, a household room
could be anywhere from ten degrees below freezing up to around 50°C. Many
safety standards require that a product does not melt, catch fire,
explode, shatter or otherwise suffer damage throughout this temperature
Room temperature should not be confused with ambient temperature, which is
even less specific. Ambient temperature can be used when conducting experiments
outdoors in mild climates — again, the assumption is that the experiment
in question is not particularly temperature sensitive.