Definition of "underwhelming"

If I grant you that the German language is spoken by the overwhelming majority of the German people you will agree with me that the best music of Germany has been composed by the underwhelming minority. Now, if the overwhelming majority of Germans are enemies, it follows that the underwhelming minority of Germans must be friendly.

1918 December 26, Musical Courier‎, volume 77

Davis, plush as ever, is a little whiny and underwhelming as Murray's girlfriend, who spends much of her time nurturing Quaid, doing his familiar sweet-natured lummox.

1990 July 13, Rita Kempley, “‘Quick Change’ (R)”, in The Washington Post‎

But in Washington and just about everywhere else, sales of "The Secret Man," Bob Woodward's story of the source known as Deep Throat, have been underwhelming.

2005 August 17, Edward Wyatt, “Sales Lag for Book on Deep Throat”, in New York Times‎

When compared with the superb ÖBB Railjet or Italy's Frecciarossa (Red Arrow), to cite just two examples, the Government-procured Intercity Express Trains (IETs) are somewhat underwhelming.

2022 March 9, Ben Jones, “RAIL Supplement: Return Ticket”, in RAIL, number 952, page 28 (supplement)