The question of just what constitutes hothousing is an interesting one. The term itself of course comes from horticulture, and in general one wouldn't think there was anything wrong with nurturing a child's mental capacities any more than carefully attempting to grow a prize rose in a weather controlled, high-nutrition environment.
However, it is almost exclusively used in a negative sense. Here's a sample:
http://giftedkids.about.com/od/glossary/g/hothouse.htmLooking at that page in particular, the negative sides to hothousing are the pushing and the idea that the child is forced to learn at such an early age that the learning process does harm in some way.
My opinion on the latter claim, that learning certain concepts earlier than normal does harm, is that it's complete horsehockey. I often see such things repeated by people who advocate late learning, such as Waldorf schooling or followers of the Moores; here's a sample:
http://www.excellenceineducation.com/better_late_than_early.phpI was interested enough to read up on this, and don't see any compelling support for the idea either that academics should actually be delayed more than they usually are in developed countries today, or that accelerating further does any harm in and of itself.
But.
Of course one can harm a child by pushing them. The harm wouldn't come as some sort of cognitive deficit-- horsehockey-- but as an aversion or opposition to learning, or simply less joy in learning, which could be just as damaging. I think children deserve to have a great deal of freedom and should be as happy as possible in their early years. So while that doesn't rule out early academics, it does mean to me that one should be exquisitely sensitive to a child's desires and back off instantly whenever necessary, and that it's far more appropriate when a child actually indicates interest in the first place.
So my longwinded answer is that it seems to fit a common-sense definition of hothousing to teach a child to read early, do early math work, etc. as an attempt to increase a child's abilities long-term; one is then raising a child as one would culture a flower, by attempting to provide an environment optimal for growth in a certain way. One might take any early hint of growth in a certain area as justification for this and point to it as "child led"-- for instance, most children naturally begin to count to some degree in early years, but most children are not then put through a math prorgram because of it. My opinion on the extent to which a particular situation involved parental pushing more than I'd personally think best would be very much based on the circumstances, but unless the child seemed unhappy I would never bring it up in any way.
In fact, the only times I would really think that a child was hothoused in the negative sens of the word-- parental pushing with possible harm to the child-- would be if the child were visibly unhappy, or if the child were really over-scheduled, i.e. always doing things the parent wanted with little or no free time. A child can of course spend her time in a number of happy ways, including learning to read, and may choose this; then it can't be hothousing.
I think a lot of parents here have had to deal with the hothousing meme, either explicitly or implicitly stated. Other parents can get very passive aggressive when they realize that their children are far behind another child in some way; their options at this point include accepting the situation, justifications for differences based on the children's interest, justifications based on parental choices in the best interests of the children who are behind, etc. Nobody likes to think they've failed their children. And of course schools can participate in this game too-- a common buzzword for school admins and teachers seems to be that children have been "worked with" or "provided many opportunities" by their parents. It might seem insulting, but I wouldn't worry about any of it as long as your child is happy and carefree.