Not at all or hardly at all. For example, He had a less than favorable view of the matter, or She had a less than adequate grasp of the subject. This expression uses less in the sense of "a smaller quantity, number, or extent than is implied," a usage dating from about a.d. 1000. The same sense appears in less than no time, a hyperbolic term for a very short time (as in Don't worry, he'll be here in less than no time) that dates from about 1800.
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