Commonly used in Mr Morrison’s native Belfast, “That’s a cracker” was the catchphrase of the late comedian Frank Carson.
However, in the US, “cracker” is seen as a racist reference to poor southern whites.
Mr Morrison, a former editor of the Sinn Féin newspaper An Phoblacht/Republican News and spokesman for the hunger striker Bobby Sands, revealed on Twitter: “In response to two tweets to me which included two pics of Adele, I said of the second, ‘That’s a cracker!’
“Next thing I knew, Twitter suspended my account and said I was in breach of its terms. I followed links on an email to appeal the suspension and what showed up is that someone had complained about my comment, ‘That’s a cracker!
“I’ve been using the term ‘cracker’ for years. There are biscuits called ‘cracker’ and even a TV series. WTF is going on?”
The ban expired on Sunday after 24 hours. It is not known who reported Morrison’s throwaway comment to Twitter.
An Irish journalist, who now covers the White House, Niall Stanage, tweeted to Mr Morrison: “I think we are having a crossing of the wires here regarding the very different meanings of ‘cracker’ in Belfast and the US.
“(In the US) it’s a pejorative/racially loaded term for a white person. From ‘whip cracker’ on plantations, I believe.”
Mr Morrison, 64, was an elected Sinn Féin politician and its director of publicity, who famously said the party wanted to “take power with a ballot box in one hand and an Armalite in the other”.
In 1990, he was jailed for the false imprisonment of an IRA informer and conspiracy to murder. Mr Morrison served five years of an eight-year sentence but the conviction was overturned in 2008.