Terrorism is a bit out of line considering that it has there is no consensus on whether the US Hiroshima and Nagasaki nuclear bombings against Japan during WWII were acts of terrorism.
terrorism, the calculated use of violence to create a general climate of fear in a population and thereby to bring about a particular political objective.
Attacking residential areas in order to instill fear in the population sounds like terrorism to me.
I would suggest you read the article I linked. Part of the Support side is that every man, woman, and child in Japan were engaged in the war effort under Total War and they were seen as military targets, rather than an unconnected population like your definition suggests. See this quote from General Curtis LeMay on why he ordered the systematic carpet bombing of Japanese cities:
"We were going after military targets. No point in slaughtering civilians for the mere sake of slaughter. Of course there is a pretty thin veneer in Japan, but the veneer was there. It was their system of dispersal of industry. All you had to do was visit one of those targets after we'd roasted it, and see the ruins of a multitude of houses, with a drill press sticking up through the wreckage of every home. The entire population got into the act and worked to make those airplanes or munitions of war ... men, women, children. We knew we were going to kill a lot of women and kids when we burned a town. Had to be done."
If this is true, then Hiroshima and Nagasaki could be construed as strikes against military targets, as the population was directly connected to the war effort.
It is interesting that many US commanders were not entirely happy with this approach of bombing the population and designating them as military targets, however, and subsequently made significant effort to warn cities with copious leaflets preceding an impending attack.
https://www.atomicheritage.org/key-documents/warning-leafletsRead this carefully as it may save your life or the life of a relative or friend. In the next few days, some or all of the cities named on the reverse side will be destroyed by American bombs. These cities contain military installations and workshops or factories which produce military goods. We are determined to destroy all of the tools of the military clique which they are using to prolong this useless war. But, unfortunately, bombs have no eyes. So, in accordance with America's humanitarian policies, the American Air Force, which does not wish to injure innocent people, now gives you warning to evacuate the cities named and save your lives.
By these actions it could also be argued that the Japanese people were given warning to evacuate and disperse, and so it was not terror. They did their best to warn and inform. They even warned them about the atomic bombs, also on that page.
Hitting infrastructure is one thing. Hitting apartment buildings is quite another. That is unless you want to argue that apartment complexes are fair game because soldiers need some place to sleep at night.
Russia has bombers and missiles with very high yield. If they wanted to cause mass civilian causality they could do so. It would be crystal clear that Russia is going after civilian deaths rather than something you have to argue about. It may be the case that Russia is indifferent to civilian casualties, but it is clear that they are not going out of their way to cause it.