I won't go into all of the details, and the problem is fixed now. But
this morning when my daughter's alarm clock went off, the electricity
was off in some rooms of the house (including the master bedroom).
some rooms had plenty of juice. One room had 2 computers running.
They are on UPSs, but the UPSs weren't beeping.

Nothing on 240V that I tested was working, except that the clothes
dryer would spin (I don't know if it was heating). Our water pump (on
120V, I think) was not working. I checked the circuit breakers, and
they were OK. After I did that, the lights came back on in 3 rooms
that had not had electricity. A TV started repeatedly trying to turn
itself on, but it couldn't, and each time it caused the lights to
blink elsewhere. I had to unplug it.

Upstairs there was a UPS, but the computer was off. The UPS had
almost no load on it, just two wall warts, I think. I noticed that if
I turned on the overhead light in the adjoining room, the UPS would
start beeping.

Some of the electrical outlets showed their usual 120V and some of
them showed only 110V.

I called the electric company and reported a partial outage. They
found the problem, saying something about "dropping a leg", and dug up
the cable in the yard and fixed the problem.

What is "dropping a leg"?

As I understand it, you have 3 wires, two of them carry 240V and the
third is a ground back to the power company. You get 120V between
either of the hot wires and the ground. Is dropping a leg related to
that?

Why would some rooms have electricity and others not, in a situation
like this?

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