雷 léi

noun
: thunder
: mine (weapon)
: (Internet slang) terrifying; terrific

Kun Reading

雷 | かみなり kaminari

noun
: thunder

雷 | いかずち OR いかづち ikazuchi

noun
: thunder

On Reading

雷 | らい rai


: thunder

Usage:

雷雲[云] lei2yun2: thundercloud [雷雲 | らいうん raiun: thunder cloud]
雷達[达] lei2da2: radar (loanword)
雷同 lei2tong2: mirroring others; identical [らいどう raido: following blindly]
雷鳴[鸣] lei2ming2: thunder; thunder rolls [雷鳴 | らいめい raimei: thunder]
雷獸 [雷兽] lei2shou4: titanothere OR Brontotheriidae, is a family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs.
[雷獣 | らいじゅう raijuu: (in Chinese mythology) beast which descends from the sky with a thunderbolt
雷雨 lei2yu3: thunderstorm [らいう raiu: thunderstorm]
雷人 lei2ren2: (Internet slang) shocking; appalling; terrifying; terrific
[雷人 | らいじん raijin: Raijin]
佈[布]雷 bu4 lei2: to lay mines
魚[鱼]雷 yu2lei2: torpedo [魚雷 | ぎょらい gyorai: torpedo]
地雷 di4lei2: landmine; (fig.) sore point; weak spot [じらい jirai: land mine]
格雷 ge2lei2: Grey; Gray
弗雷 fu2lei2: Freyr (god in Norse mythology)



Japanese common word | expression | yojijukugo 四字熟語 | idiom
雷光 | らいこう raikou: lightning

[雷魚 | はたはた hatahata: sailfin sandfish (Arctoscopus japonicus)
OR
らいぎょ raigyou: blotched snakehead (species of fish, Channa maculata)]

疾風迅雷 | しっぷうじんらい shippuu jinrai
: (yoji) with lightning speed

地震雷火事親父 | じしんかみなりかじおやじ jishin kaminari kaji oyaji
: earthquakes, thunder, fires, and fathers (as a list of things that are generally feared)



Chinese expression | chengyu 成語 | idiom
咆哮如雷 pao2 xiao4 ru2 lei2
: to be in a thundering rage

掌聲雷動 [掌声雷动] zhang3 sheng1 lei2 dong4
: thunderous applause

雷打不動 [雷打不动] lei2 da3 bu4 dong4
: not shaken by thunder; the arrangements are unalterable; to adhere rigidly to regulations; will go ahead whatever happens (of an arrangement or plan)

如雷貫耳 [如雷贯耳] ru2 lei2 guan4 er3
: lit. like thunder piercing the ear; a well-known reputation

雷公打豆腐 lei2 gong1 da3 dou4 fu5
OR
雷公打豆腐,揀軟的欺 [雷公打豆腐,拣软的欺] lei2 gong1 da3 dou4 fu5 , jian3 ruan3 de5 qi1
: the God of Thunder strikes bean curd; fig. to bully the weakest person; to pick on an easy target

黃鐘譭棄瓦釜雷鳴 [黄钟毁弃瓦釜雷鸣] huang2 zhong1 hui3 qi4 wa3 fu3 lei2 ming2
: lit. earthern pots make more noise than classical bells; good men are discarded in favor of bombastic ones

雷大雨小 lei2 da4 yu3 xiao3
OR
雷聲大,雨點小 [雷声大,雨点小] lei2 sheng1 da4 , yu3 dian3 xiao3
: loud thunder, but only tiny drops of rain (idiom); a lot of talk, but no action; action speaks louder than words; his bite is worse than his bark

Etymology:
形声 Pictophonetic.
(yu3: rain radical 173) suggests the meaning while
畾 (lei2: fields divided by dikes) provides the sound.
 
In this character 田 (tian2: fields) is a simplification of 畾, its phonetic component.



Historical Variant:
雷 thunder



Examples:

雷鳴がとどろいた。
らいめいがとどろいた raimei ga todoroita
The thunder roared.

 

参天大树,独怕雷劈。
can1tian1 da4shu4, du2 pa4 lei2 pi1
Lofty trees dread thunder.

Resources: Chinese Dictionary | Japanese Dictionary