un ‧ der ‧ whelm /ˌʌndəˈwelm $ -ər-/ BrE AmE verb [transitive]
[ Date: 1900-2000 ; Origin: under + -whelm (as in overwhelm ) ]
if you are underwhelmed by something, you do not think it is impressive – used humorously OPP overwhelm :
We were underwhelmed by the latest version of the software.