What Weaker Lofts or Weakening Lofts Means in Golf
The loft of golf clubs is expressed in degrees (21 degrees, 34 degrees, 42 degrees, whatever the case may be). The longest-hitting clubs (driver, woods, low hybrids, long irons) have the lowest lofts; the shortest-hitting clubs (short irons, wedges) have the highest lofts. So as a golfer moves through the bag, the lofts increase as the clubs get shorter.
But golfers who buy clubs off the shelf aren't always getting a great fit of golf club to their game: their swing type, their body type. That's why going to a clubfitter for a proper-fitting set of clubs is beneficial for many golfers. One of the things a clubfitter will do is ensure that the loft angles of your clubs are best-suited to your swing speed and swing path.
And that's why a golfer might weaken his or her lofts, that's why a friend or a pro might advise getting weaker lofts.
You can weaken your lofts one of several ways, including buying a new set of golf clubs. There is no industry standard for golf club lofts: A 5-iron from Company X might have a loft of 28 degrees, while Company Y's 5-iron is 27 degrees and Company Z's 5-iron is 29 degrees. So you can shop around and compare sets.
Another way to get weaker lofts is to visit a clubfitter, clubmaker, club repairer — any shop that has what is called a "loft and lie machine" — and have your lofts weakened manually. This involves very sligthly bending the hosel of the club to achieve a new loft angle. Not all clubs are bendable, however, so not every club can be adjusted in this manner.
But back to the original question, to sum up: Weakening lofts or going to weeaker lofts refers to increasing loft angle — going from, say, 27 degrees in your 5-iron to 29 degrees in your 5-iron. Weaker lofts mean (all other things being equal) getting the ball up into the air quicker, and a little higher trajectory on your shots.
Saying "you need higher lofts" or "you need more loft" is another way of saying the same thing.
What is the opposite? You can probably guess: "stronger lofts" and "strengthening lofts."