From QRZ.Com, the Icom handout, and Part 97 Of The FCC Rules -
Ham Radio Glossary - An overview of amateur radio terms.

Handi-Talkie
An amateur radio transceiver that will fit into ones hand. Usually
seen at hamfests or communications events, as they are portable, and
can go virtually anywhere. However, they tend to not be high powered,
and the battery can run down quick, if the unit is used excessively... especially at high power.

Harmful interference
Interference which endangers the functioning of a radionavigation service
or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radiocommunication service operating in accordance with the
Radio Regulations.

Harmonic

1. Children.

2. Secondary RF emission that is a multiple of the fundamental emission.

HF
"High Frequency"; generally regarded as the band of frequencies between
1.8 MHz and 30 MHz

HIHI
Telegraphy for laughter.

Homebrew
Refers to equipment that is "home built"; something you built yourself.

HPF
High Pass Filter.

HT
See Handi-Talkie.

Hz
"Hertz"; a unit used to measure frequency. Typically used with "Kilohertz" (KHz) to indicate 1,000 Hertz, or "Megahertz" (MHz) to indicate 1,000,000 Hertz.
--- SBBSecho 3.20-Win32
* Origin: The Thunderbolt BBS - Little Rock, Arkansas (1:2320/33)