コロコロlightly rolling (of a small and round thing), pleasant, high-pitched sound (e.g. bell, young woman's laughter), changing frequently (e.g. conversation, plans), (occurring) in rapid succession (e.g. sumo wrestlers being defeated), fickly, in a fickle manner, roly-poly, chirp chirp (sound of insects), ribbit ribbit (sound of frogs), croak croak, roller, lint roller, paint roller

ボールがコロコロ転(ころ)がっている。

The ball is lightly rolling. {lightly rolling (of a small and round thing), pleasant, high-pitched sound (e.g. bell, young woman's laughter), changing frequently (e.g. conversation, plans), (occurring) in rapid succession (e.g. sumo wrestlers being defeated), fickly, in a fickle manner, roly-poly, chirp chirp (sound of insects), ribbit ribbit (sound of frogs), croak croak, roller, lint roller, paint roller}

子供(こども)たちがコロコロと笑(わら)い転(ころ)げています。

The children are rolling around, laughing in a high-pitched, pleasant manner. {lightly rolling (of a small and round thing), pleasant, high-pitched sound (e.g. bell, young woman's laughter), changing frequently (e.g. conversation, plans), (occurring) in rapid succession (e.g. sumo wrestlers being defeated), fickly, in a fickle manner, roly-poly, chirp chirp (sound of insects), ribbit ribbit (sound of frogs), croak croak, roller, lint roller, paint roller}

話(はなし)がコロコロと変(か)わるから、追(お)いつくのが大変(たいへん)だ。

Because the conversation changes frequently, it's hard to keep up. {lightly rolling (of a small and round thing), pleasant, high-pitched sound (e.g. bell, young woman's laughter), changing frequently (e.g. conversation, plans), (occurring) in rapid succession (e.g. sumo wrestlers being defeated), fickly, in a fickle manner, roly-poly, chirp chirp (sound of insects), ribbit ribbit (sound of frogs), croak croak, roller, lint roller, paint roller}

コロコロと丸(まる)い赤(あか)ちゃんは、いつも沢山(たくさん)食(た)べているのだろう。

The roly-poly baby must always be eating a lot. {lightly rolling (of a small and round thing), pleasant, high-pitched sound (e.g. bell, young woman's laughter), changing frequently (e.g. conversation, plans), (occurring) in rapid succession (e.g. sumo wrestlers being defeated), fickly, in a fickle manner, roly-poly, chirp chirp (sound of insects), ribbit ribbit (sound of frogs), croak croak, roller, lint roller, paint roller}

あまり笑(わら)わない父(ちち)がコロコロと笑(わら)っているところを見(み)てビックリしました。

I was surprised to see my father, who rarely laughs, laughing in a roly-poly manner. {lightly rolling (of a small and round thing), pleasant, high-pitched sound (e.g. bell, young woman's laughter), changing frequently (e.g. conversation, plans), (occurring) in rapid succession (e.g. sumo wrestlers being defeated), fickly, in a fickle manner, roly-poly, chirp chirp (sound of insects), ribbit ribbit (sound of frogs), croak croak, roller, lint roller, paint roller}