Say in my main.less file which gets compiled into main.css, I have the following:
.section1 {
    .col-xs-1, .col-sm-1, .col-md-1, .col-lg-1,
    .col-xs-2, .col-sm-2, .col-md-2, .col-lg-2,
    .col-xs-3, .col-sm-3, .col-md-3, .col-lg-3,
    .col-xs-4, .col-sm-4, .col-md-4, .col-lg-4,
    .col-xs-5, .col-sm-5, .col-md-5, .col-lg-5,
    .col-xs-6, .col-sm-6, .col-md-6, .col-lg-6, 
    .col-xs-7, .col-sm-7, .col-md-7, .col-lg-7,
    .col-xs-8, .col-sm-8, .col-md-8, .col-lg-8,
    .col-xs-9, .col-sm-9, .col-md-9, .col-lg-9,
    .col-xs-10, .col-sm-10, .col-md-10, .col-lg-10,
    .col-xs-11, .col-sm-11, .col-md-11, .col-lg-11,
    .col-xs-12, .col-sm-12, .col-md-12, .col-lg-12
    {
        border: 1px solid green;
    }
}
.section2 {
    .col-xs-1, .col-sm-1, .col-md-1, .col-lg-1,
    .col-xs-2, .col-sm-2, .col-md-2, .col-lg-2,
    .col-xs-3, .col-sm-3, .col-md-3, .col-lg-3,
    .col-xs-4, .col-sm-4, .col-md-4, .col-lg-4,
    .col-xs-5, .col-sm-5, .col-md-5, .col-lg-5,
    .col-xs-6, .col-sm-6, .col-md-6, .col-lg-6, 
    .col-xs-7, .col-sm-7, .col-md-7, .col-lg-7,
    .col-xs-8, .col-sm-8, .col-md-8, .col-lg-8,
    .col-xs-9, .col-sm-9, .col-md-9, .col-lg-9,
    .col-xs-10, .col-sm-10, .col-md-10, .col-lg-10,
    .col-xs-11, .col-sm-11, .col-md-11, .col-lg-11,
    .col-xs-12, .col-sm-12, .col-md-12, .col-lg-12
    {
        border: 1px solid red;
    }
}
Clearly this is already becoming unwieldy, excessively cluttering my main.less file and adding duplication of sorts which could cause multiple unnecessary changes.
How can I improve this? Is there a way I could for example do something like this:
.allCellTypes 
{
    .col-xs-1, .col-sm-1, .col-md-1, .col-lg-1,
    .col-xs-2, .col-sm-2, .col-md-2, .col-lg-2,
    .col-xs-3, .col-sm-3, .col-md-3, .col-lg-3,
    .col-xs-4, .col-sm-4, .col-md-4, .col-lg-4,
    .col-xs-5, .col-sm-5, .col-md-5, .col-lg-5,
    .col-xs-6, .col-sm-6, .col-md-6, .col-lg-6, 
    .col-xs-7, .col-sm-7, .col-md-7, .col-lg-7,
    .col-xs-8, .col-sm-8, .col-md-8, .col-lg-8,
    .col-xs-9, .col-sm-9, .col-md-9, .col-lg-9,
    .col-xs-10, .col-sm-10, .col-md-10, .col-lg-10,
    .col-xs-11, .col-sm-11, .col-md-11, .col-lg-11,
    .col-xs-12, .col-sm-12, .col-md-12, .col-lg-12
}
.section1 .allCellTypes 
{
    border: 1px solid green;
}
.section2 .allCellTypes 
{
    border: 1px solid red;
}
Thanks
Edit 1: As per @Alessandro Minoccheri's suggestion, I compiled but the resulting css was as follows:
.section1 .allCellTypes 
{
    border: 1px solid green;
}
.section2 .allCellTypes 
{
    border: 1px solid red;
}
Any mention of the classes that would be covered by .allCellTypes are completely omitted. Perhaps there are two reasons for this? 
- The definitions for the classes which would be grouped into 
.allCellTypesare defined elsewhere (within compiled bootstrap files). - I compile the 
.lessfiles using lessphp, perhaps it has a bug? 
Edit 2: I placed the following code in the demo window on the lessphp page...
.cell1 {
  background-color: red;
}
.cell2 {
  background-color: green;
}
.cell3 {
  background-color: blue;
}
.allCellTypesClass {
  .cell1;
  .cell2;
  .cell3;
}
.section1 {
  .allCellTypes {
    .allCellTypesClass;
    border: 1px solid red;
  }
}
and I got the following result:
.cell1 {
  background-color: red;
}
.cell2 {
  background-color: green;
}
.cell3 {
  background-color: blue;
}
.allCellTypesClass {
  background-color: red;
  background-color: green;
  background-color: blue;
}
.section1 .allCellTypes {
  background-color: red;
  background-color: green;
  background-color: blue;
  border: 1px solid red;
}
So I'm afraid your answer, @Alessandro Minoccheri, is not doing what I wanted!
                        
The gist of what I do is as follows:
My Mixin:
Applying:
If you don't want to affect nested columns, then:
If you only want a certain column breakpoint:
If you don't want to affect forms (haven't tested this but should work fine).